Zoom lens system and image pickup apparatus using the same

ABSTRACT

A zoom lens system includes in order from an object side to an image side, a first lens unit G 1  having a positive refracting power, a second lens unit G 2  having a negative refracting power, a third lens unit G 3  having a positive refracting power, and a fourth lens unit G 4  having a positive refracting power. At the time of zooming from a wide angle end to a telephoto end, distances between the lens units change. The third lens unit includes a first cemented lens component having a concave image-side surface on the image side, and a second cemented lens component having a concave object-side surface on the object side, which is disposed immediately after the image side of the first cemented lens component. The first cemented lens component includes a positive lens, and a negative lens having a concave image-side surface which is disposed on the image side of the positive lens. The second cemented lens component includes a negative lens having a concave object-side surface on the object side, and a positive lens which is disposed on the image side of the negative lens.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2009-063961 filed on Mar.17, 2009; the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system. Moreover, thepresent invention relates to an image pickup apparatus including a videocamera and a digital camera.

2. Description of the Related Art

In recent years, replacing a camera in which, a film is used, a digitalcamera in which, an object is photographed by using an image pickupelement such as a CCD (Charge Coupled Device) and a CMOS (ComplementaryMetal Oxide Semiconductor) sensor has become mainstream.

Furthermore, there are several categories of digital cameras in a widerange from a high-function type for professional use to a compactpopular type.

From among these categories, a user of a digital camera of the populartype seeks to enjoy photography by capturing readily various scenes atany time and anywhere. Therefore, a digital camera having a small size,and which can be carried conveniently is preferred.

For carrying out slimming and small-sizing, an image pickup element isto be made small. Here, in an image pickup element which is small-size,for letting the number of pixels to be same as the number of pixels ofthe image pickup element before small-sizing, it is necessary to make apitch of pixels small. Therefore, in the image pickup element which issmall-size, insufficiency of sensitivity has to be covered by an opticalsystem. Consequently, an optical system having a bright F value isnecessary.

Whereas, a zooming ratio of about three times and an angle of field at awide angle end of about 63° of a zoom lens system which is used in adigital camera of a compact type, are common.

As such optical system, an optical system which includes in order froman object side, a first lens unit having a positive refracting power, asecond lens unit having a negative refracting power, a third lens unithaving a positive refracting power, and a fourth lens unit having apositive refracting power, and in which, distances between the lensunits change at the time of zooming from a wide angle end to a telephotoend, has been known. An example of a conventional technology of suchoptical system is disclosed in Japanese Patent Application Laid-openPublication Nos. 2004-252204, 2003-315676, and 2001-242379.

A zoom lens system disclosed in Japanese Patent Application Laid-openPublication No. 2004-252204 is a zoom lens system in which, the F valueis about 2.8 at the wide angle end, the zooming ratio is about three,and the angle of field at the wide angle end is about 63°.

A zoom lens system disclosed in Japanese Patent Application Laid-openPublication No. 2003-315676 is a zoom lens system in which, the zoomingratio of four and more has been secured, but the F value is about 2.8 atthe wide angle end, and the angle of field at the wide angle end isabout 63°.

A zoom lens system disclosed in Japanese Patent Application Laid-openPublication No. 2001-242279, is a comparatively bright zoom lens systemhaving the F value of about 2.0 at the wide angle end, but is a zoomlens system having the zooming ratio of about three, and the angle offield at the wide angle end of about 63°.

SUMMARY OF THE INVENTION

To solve the abovementioned problems, and to achieve the object, a zoomlens system according to the present invention comprises in order froman object side to an image side

a first lens unit having a positive refracting power,

a second lens unit having a negative refracting power,

a third lens unit having a positive refracting power, and

a fourth lens unit having a positive refracting power, and

at the time of zooming from a wide angle end to a telephoto end,distances between the lens units change, and

the third lens unit comprises a first cemented lens component having aconcave image-side surface on the image side, and a second cemented lenscomponent having a concave object-side surface on the object side, whichis disposed immediately after the image side of the first cemented lenscomponent, and

the first cemented lens component includes a positive lens, and anegative lens having a concave image-side surface which is disposed onthe image side of the positive lens, and

the second cemented lens component includes a negative lens having aconcave object-side surface on the object side, and a positive lenswhich is disposed on the image side of the negative lens.

Moreover, an image pickup apparatus according to another aspect of thepresent invention comprises

the abovementioned zoom lens system, and

an image pickup element, which is disposed on an image side of the zoomlens system, and which converts an image formed by the zoom lens system,to an electric image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A, FIG. 1B, and FIG. 1C are lens cross-sectional views at a timeof infinite object point focusing of a first embodiment of a zoom lenssystem of the present invention, where, FIG. 1A shows a state at a wideangle end, FIG. 1B shows an intermediate focal length state, and FIG. 1Cshows a state at a telephoto end;

FIG. 2A, FIG. 2B, and FIG. 2C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a second embodiment of the zoom lens systemof the present invention;

FIG. 3A, FIG. 3B, and FIG. 3C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a third embodiment of the zoom lens systemof the present invention;

FIG. 4A, FIG. 4B, and FIG. 4C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a fourth embodiment of the zoom lens systemof the present invention;

FIG. 5A, FIG. 5B, and FIG. 5C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a fifth embodiment of the zoom lens systemof the present invention;

FIG. 6A, FIG. 6B, and FIG. 6C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a sixth embodiment of the zoom lens systemof the present invention;

FIG. 7A, FIG. 7B, and FIG. 7C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a seventh embodiment of the zoom lenssystem of the present invention;

FIG. 8A, FIG. 8B, and FIG. 8C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of an eighth embodiment of the zoom lenssystem of the present invention;

FIG. 9A, FIG. 9B, and FIG. 9C are diagrams similar to FIG. 1A, FIG. 1B,and FIG. 1C respectively, of a ninth embodiment of the zoom lens systemof the present invention;

FIG. 10A, FIG. 10B, and FIG. 10C are diagrams similar to FIG. 1A, FIG.1B, and FIG. 1C respectively, of a tenth embodiment of the zoom lenssystem of the present invention;

FIG. 11A, FIG. 11B, and FIG. 11C are diagrams similar to FIG. 1A, FIG.1B, and FIG. 1C respectively, of an eleventh embodiment of the zoom lenssystem of the present invention;

FIG. 12A, FIG. 12B, and FIG. 12C are aberration diagrams at the time ofinfinite object point focusing, of the first embodiment;

FIG. 13A, FIG. 13B, and FIG. 13C are aberration diagrams at the time ofinfinite object point focusing, of the second embodiment;

FIG. 14A, FIG. 14B, and FIG. 14C are aberration diagrams at the time ofinfinite object point focusing, of the third embodiment;

FIG. 15A, FIG. 15B, and FIG. 15C are aberration diagrams at the time ofinfinite object point focusing, of the fourth embodiment;

FIG. 16A, FIG. 16B, and FIG. 16C are aberration diagrams at the time ofinfinite object point focusing, of the fifth embodiment;

FIG. 17A, FIG. 17B, and FIG. 17C are aberration diagrams at the time ofinfinite object point focusing, of the sixth embodiment;

FIG. 18A, FIG. 18B, and FIG. 18C are aberration diagrams at the time ofinfinite object point focusing of the seventh embodiment;

FIG. 19A, FIG. 19B, and FIG. 19C are aberration diagrams at the time ofinfinite object point focusing of the eighth embodiment;

FIG. 20A, FIG. 20B, and FIG. 20C are aberration diagrams at the time ofinfinite object point focusing of the ninth embodiment;

FIG. 21A, FIG. 21B, and FIG. 21C are aberration diagrams at the time ofinfinite object point focusing of the tenth embodiment;

FIG. 22A, FIG. 22B, and FIG. 22C are aberration diagrams at the time ofinfinite object point focusing of the eleventh embodiment;

FIG. 23 is a diagram describing a correction of distortion;

FIG. 24 is a front perspective view showing an appearance of a digitalcamera in which, a zoom lens system according to the present inventionis incorporated;

FIG. 25 is a rear perspective view of the digital camera;

FIG. 26 is a cross-sectional view of the digital camera; and

FIG. 27 is a structural block diagram of an internal circuit of maincomponents of a digital camera.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A zoom lens system according to a first aspect of the present inventionincludes in order from an object side to an image side

a first lens unit having a positive refracting power, a second lens unithaving a negative refracting power, a third lens unit having a positiverefracting power, and a fourth lens unit having a positive refractingpower, and

at the time of zooming from a wide angle end to a telephoto end,distances between the lens units change, and

the third lens unit includes a first cemented lens component (L₃₂)having a concave image-side surface on the image side, and a secondcemented lens component (L₃₃) having a concave object-side surface onthe object side, which is disposed immediately after the image side ofthe first cemented lens component, and

the first cemented lens component (L₃₂) includes a positive lens(L_(32p)), and a negative lens (L_(32n)) having a concave image-sidesurface which is disposed on the image side of the positive lens, and

the second cemented lens component (L₃₃) includes a negative lens(L_(33n)) having a concave object-side surface on the object side, and apositive lens (L_(33p)) which is disposed on the image side of thenegative lens.

A lens component means a lens body which is divided by a refractingsurface in contact with air, and a cemented lens component means a lensbody having a refracting surface of a cemented surface in the lenscomponent.

Moreover, signs indicated in brackets are signs which are associatedwith the corresponding lens components and lenses in the embodiments.However, a technological range of the present invention is notrestricted by the embodiments.

A reason for and an effect of adopting such arrangement will bedescribed below.

In the present invention, for making it easy to secure a sufficientzooming ratio, an arrangement which includes in order from the objectside, a first lens unit having a positive refracting power, a secondlens unit having a negative refracting power, a third lens unit having apositive refracting power, and a fourth lens unit having a positiverefracting power, and in which, zooming is carried out from the wideangle end to the telephoto end by changing distances between the lensunits is adopted.

By adopting such an arrangement, it is possible to secure a zoomingfunction of the second lens unit and the third lens unit, and to preventan amount of movement of each lens unit from becoming substantial whilesuppressing an a fluctuation in aberration at the time of zooming,thereby leading to a compactness of an optical system.

In this arrangement, in the third lens unit, an axial light beam becomesthick as compared to an axial light beam in the other lens units.Therefore, for achieving an optical system in which, the F value isbrightened, it is effective to let an arrangement which enables to carryout a favorable aberration correction in the third lens unit.

Therefore, in the present invention, the third lens unit is let to havean arrangement having the first cemented lens component having theconcave image-side surface on the image side, and the second cementedlens component having the concave object-side surface which is disposedimmediately after the image side of the first cemented lens component.Moreover, the first cemented lens component includes the positive lens,and the negative lens having a concave image-side surface which isdisposed on the image side of the positive lens, and the second cementedlens component includes the negative lens having a concave object-sidesurface on the object side, and the positive lens which is disposed onthe image side of the negative lens.

By making such an arrangement, it is possible to make small a curvatureof each lens surface or a refracting power of each lens in the thirdlens unit, and accordingly, it is possible to suppress an occurrence ofaberration. Moreover, an arrangement is let to be such that a surface onthe image side of the first cemented lens component and a surface on theobject side of the second cemented lens component are facing concavesurfaces, and the arrangement is let to be the abovementioned lensarrangement. Accordingly, a spherical aberration, a chromaticaberration, and Petzval's sum from the wide angle end up to thetelephoto end can be corrected favorably. Moreover, it is advantageousfor securing brightness, an angle of field, and a zooming ratio.

Furthermore, in the zoom lens system of the present invention, it ispreferable that

the first cemented lens component has a meniscus shape convex to theobject side, and

the second cemented lens component has a meniscus shape convex to theimage side.

By making such an arrangement, a symmetry of the first cemented lenscomponent and the second cemented lens components is more favorable, andit is advantageous for shortening the overall length and for securingthe zooming ratio by securing the positive refracting power of the thirdlens unit.

Moreover, in the abovementioned invention, it is preferable that thefirst cemented lens component and the second cemented lens componentsatisfy the following conditional expression (1).

−0.9<SF _(3n)<−0.1   (1)

where,

SF_(3n) is defined by SF_(3n)=(32R_(1r)+33R_(2f))/(32R_(1r)−33R_(2f)),where

32R_(1r) denotes a radius of curvature on the image side of the firstcemented lens component in the third lens unit, and

33R_(2f) denotes a radius of curvature on the object side of the secondcemented lens component in the third lens unit.

Conditional expression (1) is an expression which specifies a preferableshape factor of an air lens having a biconvex shape which is formed bythe first cemented lens component and the second cemented lenscomponent.

By making an arrangement such that a lower limit in conditionalexpression (1) is not surpassed, a negative refracting power of asurface on the object side of the second cemented lens component issecured. Accordingly, the negative refracting power can be divided(shared) favorably with the surface on the object side of the firstcemented lens component. As a result, it is advantageous for reductionof a high-order aberration such as the spherical aberration when thebrightness is secured.

By making an arrangement such that an upper limit in conditionalexpression (1) is not surpassed, the negative refracting power of thesurface on the object side of the second cemented lens component issuppressed to be moderate. Accordingly, it becomes easy to impart asufficient positive refracting power to the third lens unit, and it isadvantageous for small sizing, making zooming ratio high, and making afocal length short.

Moreover, a zoom lens system according to a second aspect for solvingthe abovementioned problems includes

in order from an object side to an image side, a first lens unit havinga positive refracting power, a second lens unit having a negativerefracting power, a third lens unit having a positive refracting power,and a fourth lens unit having a positive refracting power, and

at the time of zooming from a wide angle end to a telephoto end,distances between the lens units change, and

the third lens unit includes a first cemented lens component (L₃₂), anda second cemented lens component (L₃₃) which is disposed on the imageside of the first cemented lens component (L₃₂), and

the first cemented lens component (L₃₂) includes a positive lens(L_(32p)), and a negative lens (L_(32n)) which is disposed on the imageside of the positive lens (L_(32p)), and

the second cemented lens component (L₃₃) includes a negative lens(L_(33n)) and a positive lens (L_(33p)) which is disposed on the imageside of the negative lens (L_(33n)), and

the first cemented lens component (L₃₂) and the second cemented lenscomponent (L₃₃) satisfy the following conditional expression (2).

50<νd₃<120   (2)

where,

νd₃ is defined by νd₃=(νdL_(32p)+νdL_(33p))−(νdL_(32n)+νdL_(33n))

where,

νdL_(32p) denotes Abbe constant for d-line of the positive lens of thefirst cemented lens component in the third lens unit,

νdL_(33p) denotes Abbe constant for d-line of the positive lens of thesecond cemented lens component in the third lens unit,

νdL_(32n) denotes Abbe constant for d-line of the negative lens of thefirst cemented lens component in the third lend unit, and

νdL_(33n) denotes Abbe constant for d-line of the negative lens of thesecond cemented lens component in the third lens unit.

An effect which is same as in the zoom lens system according to theabovementioned first aspect will be omitted.

Conditional expression (2) is an expression which specifies a glassmaterial which is preferable for a correction of the chromaticaberration, and particularly, for a correction of a longitudinalchromatic aberration which becomes conspicuous when the brightness issecured.

For correction favorably within the third lens unit, the chromaticaberration which occurs due to a substantial positive refracting powerin the third lens unit, it is effective to use a glass material having acomparatively small chromatic dispersibility in an appropriate range forthe positive lens in the second cemented lens component, and to use aglass material having a comparatively substantial chromaticdispersibility in an appropriate range for the negative lens in thesecond cemented lens component.

Concretely, it is effective to let a difference between the Abbe'snumber for the positive lens and the Abbe's number for the negative lensto be conditional expression (2).

By making an arrangement such that a lower limit in conditionalexpression (2) is not surpassed, it is advantageous for correction ofthe chromatic aberration, for securing a sufficient optical performance,and for designing a zoom lens system having an improved performance.

Even in the zoom lens system according to the abovementioned firstaspect, it is preferable that the first cemented lens component and thesecond cemented lens component satisfy the abovementioned conditionalexpression (2).

In one of the abovementioned zoom lens systems, it is preferable thatone of the following arrangements is satisfied simultaneously.

It is preferable that the first cemented lens component and the secondcemented lens component are disposed side-by-side living a space betweenthe first cemented lens component and the second cemented lenscomponent, and satisfy the following conditional expression (3).

0.08<D ₃ /f ₃<0.20   (3)

where,

D₃ denotes a distance on an optical axis between the first cemented lenscomponent and the second cemented lens component in the third lens unit,and

f₃ denotes a focal length of the third lens unit.

Conditional expression (3) is an expression which specifies a preferableair distance between the surface on the image side of the first cementedlens component and the surface on the object side of the second cementedlens component.

By making an arrangement such that a lower limit in conditionalexpression (3) is not surpassed, an axial distance between the firstcemented lens component and the second cemented lens component issecured. Accordingly, it is advantageous for reduction of variousaberrations in the third lens unit, and it becomes easy to achieve afavorable image forming performance.

By making an arrangement such that an upper limit in conditionalexpression (3) is not surpassed, an axial thickness of the third lensunit can be suppressed easily, which is advantageous for small sizing.

Moreover, it is preferable that the second cemented lens component isdisposed nearest to the image side, in the third lens unit, and thepositive lens in the second cemented lens component has an asphericimage-side surface which is convex on the image side.

By letting a surface of emergence nearest to the image side of the thirdlens unit to be an aspheric surface, a correction of coma aberrationwhich occurs off-axis becomes easy, and it is easy to achieve afavorable image forming performance.

Moreover, by letting the aspheric surface to have a convex shape, it ispossible to reduce an effect on the image forming performance due to amanufacturing error.

Moreover, it is preferable that the lens unit includes in order from theobject side, a positive single lens (L₃₁) having a positive refractingpower, the first cemented lens component (L₃₂), and the second cementedlens component (L₃₃), and the positive single lens (L₃₁) includes atleast one aspheric surface.

By disposing a single lens having a positive refracting power nearest tothe object side of the third lens unit, it is possible to make furthersmaller the refracting power of each lens or a curvature of each lenssurface in the third lens unit. Accordingly, it is possible to suppressan occurrence of aberration. Moreover, by letting the single lens havinga positive refracting power to have at least one aspheric surface, it ispossible to correct more effectively the spherical aberration whichoccurs in the third lens unit.

Moreover, it is preferable that the zoom lens system satisfies thefollowing conditional expressions (4) and (5).

0.26<UY _(1G) /f _(w)<0.28   (4)

0.25<UY _(3G) /f ₃<0.5   (5)

where,

f_(w) denotes a focal length of the overall zoom lens system at the wideangle end,

UY_(1G) denotes a height from an optical axis of axial marginal lightrays at a surface on the object side of the first lens unit, at the wideangle end,

UY_(3G) denotes a height from an optical axis of axial marginal rays ata surface on the object side of the third lens unit, at the wide angleend, and

f₃ is a focal length of the third lens unit.

Conditional expression (4) is an expression related to a preferable Fvalue at the wide angle end.

By making an arrangement such that a lower limit in conditionalexpression (4) is not surpassed, it is advantageous for reduction of anoise in an image and for photographing an image having a low focaldepth.

By making an arrangement such that an upper limit in conditionalexpression (4) is not surpassed, it is advantageous for reducing thenumber of lenses for securing the image forming performance.

Conditional expression (5) is a preferable condition for making it easyto adjust appropriately an amount of aberration which occurs in thethird lens unit.

By making an arrangement such that a lower limit in conditionalexpression (5) is not surpassed, it is easy to secure brightness whichsatisfies conditional expression (4).

By making an arrangement such that a higher limit in conditionalexpression (5) is not surpassed, it is possible to make small aneffective diameter of the third lens unit, to carry out the aberrationcorrection easily, and it is advantageous for securing the favorableimage forming performance with conditional expression (4) alreadysatisfied.

An arrangement may be made such that the following conditionalexpression (6) is satisfied instead of conditional expression (5), or,in addition to conditional expression (5).

0.60<UY _(3G) /f _(w)<1.00   (6)

where,

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end, and

UY_(3G) denotes the height from an optical axis of axial marginal raysat a surface on the object side of the third lens unit, at the wideangle end.

By making an arrangement such that a lower limit in conditionalexpression (6) is not surpassed, it is easy to secure the brightnesswhich satisfies conditional expression (4).

By making an arrangement such that an upper limit in conditionalexpression (6) is not surpassed, it is possible to make small theeffective diameter of the third lens unit, and it becomes easy to carryout the aberration correction, and it is advantageous for securing thefavorable image forming performance with conditional expression (4)already satisfied.

When the zoom lens system includes a focusing mechanism, although thecorresponding values of the conditional expression change, in this case,the corresponding values are let to be values in a state of beingfocused at the farthest distance. Moreover, when it is possible toadjust the brightness, values are let to be values in a brightest state.Similar is a case for the following conditional expressions.

For achieving an efficient and favorable optical performance whilerealizing compactness, it is preferable that the zoom lens system of thepresent invention satisfies one of the following arrangements apart fromthe abovementioned arrangements.

From a point of view of balance of the optical performance andcompactness, it is preferable that the following conditional expression(7) is satisfied for the refracting power of the first lens unit.

7.0<f ₁ /f _(w)<10   (7)

where,

f₁ denotes a focal length of the first lens unit, and

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end.

By making an arrangement such that a lower limit in conditionalexpression (7) is not surpassed, it is possible to reduce an occurrenceof aberration at the wide angle end by suppressing the refracting powerof the first lens unit, which becomes advantageous for securing thefavorable optical performance.

By making an arrangement such that an upper limit in conditionalexpression (7) is not surpassed, it is advantageous for compactness ofthe overall length of the zoom system by securing the refracting powerof the first lens unit, and presumably for compactness of a lens barrel.

Regarding a refracting power of the second lens unit, it is preferablethat the following conditional expressions (8) and (9) are satisfied.

1.6<|f ₂ /f _(w)|<2.1   (8)

3.5<(β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))<5.0   (9)

where,

f₂ denotes a focal length of the second lens unit,

f_(w) denotes the focal length of the overall zoom lens system at thewide angel end,

β_(2w) and β_(2t) denote a lateral magnification of the second lensunit, at the wide angle end and the telephoto end respectively,

β_(3w) and β_(3t) denote a lateral magnification of the third lens unit,at the wide angle end and the telephoto end respectively, and

β_(4w) and β_(4t) denote a lateral magnification of the fourth lensunit, at the wide angle end and the telephoto end respectively.

Conditional expression (9) is an expression which specifies a preferablezooming ratio in a system from the first lens unit up to the fourth lensunit.

By making an arrangement such that a lower limit in conditionalexpression (9) is not surpassed, it is advantageous for securing thezooming ratio of the overall zoom lens system, and it is possible toadjust to an angle of field of photography corresponding to variousphotographic scenes.

By making an arrangement such that an upper limit in conditionalexpression (9) is not surpassed, it is easy to reduce an amount ofmovement of the lens units, and it is advantageous for making the sizesmall while suppressing a fluctuation in aberration.

By making an arrangement such that a lower limit in conditionalexpression (8) is not surpassed, the negative refracting power issuppressed to be moderate, and it is advantageous for aberrationcorrection.

By making an arrangement such that conditional expression (9) issatisfied and an upper limit in conditional expression (8) is notsurpassed, it is possible to secure sufficiently the negative refractingpower of the second lens unit, and it is advantageous for reduction ofthe amount of movement for the zooming, and presumably, for compactnessof the lens barrel.

Regarding a refracting power of the third lens unit, it is preferablethat the following conditional expression (10) is satisfied.

2.0<f ₃ /f _(w)<3.0   (10)

where,

f₃ denotes the focal length of the third lens unit, and

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end.

By making an arrangement such that a lower limit in conditionalexpression (10) is not surpassed, the refracting power of the third lensunit is suppressed to be moderate, and it is advantageous for theaberration correction.

By making an arrangement such that an upper limit in conditionalexpression (10) is not surpassed, it is possible to secure a zoomingeffect in the third lens unit, and it is advantageous for shortening theoverall length at the time of zooming to the telephoto end. Moreover, itbecomes easy to suppress an amount of fluctuation in an exit-pupilposition. Accordingly, it is easy to suppress an adverse effect onshading which is due to a fluctuation in an angle of incidence on animage pickup element such as a CCD at an off-axis image-plane position.

Regarding a refracting power of the fourth lens unit, it is preferablethat the following conditional expression (11) is satisfied.

3.4<f ₄ /f _(w)<5.5   (11)

where,

f₄ denotes a focal length of the fourth lens unit, and

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end.

By making an arrangement such that a lower limit in conditionalexpression (11) is not surpassed, and by making an arrangement such thatan upper limit in conditional expression (11) is not surpassed, therefracting power of the fourth lens unit becomes appropriate, and itbecomes easy to suppress an excessive correction and an insufficientcorrection of an astigmatism and a distortion in a total zoom range.

The fourth lens unit may be formed of a plastic material. A mainfunction of the fourth lens unit is to make incidence light raysefficiently on an electronic image pickup element such as a CCD and aCMOS by disposing the exit-pupil position at an appropriate position.For such function, when a power is set within a range as in theabovementioned conditional expression (9), a comparatively substantialpower is not necessary, and it is also possible to form the fourth lensunit by using a glass material having a low refractive index, such as aplastic lens.

When a plastic lens is used in the fourth lens unit, a cost issuppressed to be low, and it is possible to provide a zoom lens systemat a low cost.

Regarding the overall length of the zoom length system for the focallength of the overall zoom lens system at the wide angle end, it ispreferable that the following conditional expression (12) is satisfied.

9.0<L _(w) /f _(w)<10.2   (12)

where,

L_(w) denotes a distance along an optical axis from a surface on theobject side of the first lens unit up to an image plane at the wideangle end when a back focus is let to be an air conversion distance, and

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end.

By making an arrangement such that a lower limit in conditionalexpression (12) is not surpassed, it is possible to secure a distancebetween the second lens unit and the third lens unit, and it isadvantageous for securing a space for zooming.

By making an arrangement such that an upper limit in conditionalexpression (12) is not surpassed, the overall length of the zoom lenssystem at the wide angle end is suppressed, and it is advantageous forsmall sizing in a direction of thickness of the lens barrel. Moreover,it is possible to lower a height of light rays in the first lens unit,and it is advantageous for making a lens diameter small.

Moreover, it is preferable that the second lens unit includes in orderfrom the object side, a negative meniscus lens component, a negativelens component, and a positive lens component.

By making such an arrangement, thereby by bringing positions ofprincipal points of the second lens unit toward the image side, it iseasy to secure space for zooming at the telephoto end. Moreover, it ispossible to make high a lateral magnification in the second lens unit,which is advantageous for securing a zooming effect by the second lensunit.

At this time, regarding a proportion of the zooming effect of the secondlens unit and the third lens unit, it is preferable that the followingconditional expression (13) is satisfied.

0.5<(β_(2t)/β_(2w))/(β_(3t)/β_(3w))<1.0   (13)

3.5<(β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))<5.0   (9)

where,

β_(2w) and β_(2t) denote a lateral magnification of the second lensunit, at the wide angle end and the telephoto end respectively,

β_(3w) and β_(3t) denote a lateral magnification of the third lens unit,at the wide angle end and the telephoto end respectively, and

β_(4w) and β_(4t) denote a lateral magnification of the fourth lensunit, at the wide angle end and the telephoto end respectively.

The description of conditional expression (9) will be omitted as it hasalready being described.

By making an arrangement such that a lower limit in conditionalexpression (13) is not surpassed, it is easy to suppress an amount ofmovement of the third lens unit, and it is advantageous for making abarrel size small. Moreover, it is easy to suppress the refracting powerof the third lens unit, and it is advantageous for correction ofaberration, particularly, a longitudinal aberration such as thespherical aberration at the telephoto end.

By making an arrangement such that conditional expression (9) issatisfied, and an upper limit in conditional expression (13) is notsurpassed, it is possible to reduce a zooming load of the second lensunit, and it is easy to suppress an increase in the overall length, andan increase in a diameter of a front lens. Moreover, it is advantageousfor correction of an aberration by the second lens unit, such as acorrection of various longitudinal aberrations such as a curvature offield and the chromatic aberration of magnification at the telephotoend.

Regarding a zooming effect of the second lens unit, it is preferablethat the following conditional expression (14) is satisfied.

1.4<β_(2t)/β_(2w)<2.1   (14)

where,

β_(2w) and β_(2t) denote lateral magnification of the second lens unit,at the wide angle end and the telephoto end respectively.

By making an arrangement such that a lower limit in conditionalexpression (14) is not surpassed, it is easy to suppress a load of azooming effect on the other lens units. By suppressing the zooming loadof the third lens unit, it is easy to suppress an occurrence of thelongitudinal aberration such as the spherical aberration at thetelephoto end. By suppressing the zooming load of the fourth lens unit,it is possible to make small the refracting power of the fourth lensunit to be moderate, and it is advantageous for reduction of theastigmatism over the entire area.

By making an arrangement such that an upper limit in conditionalexpression (14) is not surpassed, it becomes easy to suppress therefracting power of the second lens unit. Accordingly, it becomes easyto suppress the occurrence of an aberration, particularly variousoblique aberrations in the second lens unit, such as the chromaticaberration of magnification and the curvature of field at the telephotoend.

Moreover, regarding the zooming effect of the third lens unit, it ispreferable that the following conditional expression (15) is satisfied.

1.8<β_(3t)/β_(3w)<2.9   (15)

where,

β_(3w) and β_(3t) denote a lateral magnification of the third lens unit,at the wide angle end and the telephoto end respectively.

By making an arrangement such that a lower limit in conditionalexpression (15) is not surpassed, it becomes easy to suppress the loadof the zooming effect of the other lens units. By suppressing thezooming load of the second lens unit, it becomes easy to suppress theoccurrence of various oblique aberrations such as the chromaticaberration of magnification and the curvature of field at the telephotoend. By suppressing the zooming load of the fourth lens unit, it ispossible to make small the refracting power of the fourth lens unit tobe moderate, and it is advantageous for reduction of astigmatism overthe entire range.

By making an arrangement such that an upper limit in conditionalexpression (15) is not surpassed, it becomes easy to suppress therefracting power of the third lens unit. Accordingly, it becomes easy tosuppress the occurrence of aberration in the third lens unit,particularly the longitudinal aberration such as the sphericalaberration at the telephoto end.

Moreover, regarding the zooming effect of the fourth lens unit, it ispreferable that the following conditional expression (16) is satisfied.

0.6<β_(4t)/β_(4w)<1.3   (16)

where,

β_(4w) and β_(4t) denote a lateral magnification of the fourth lensunit, at the wide angle end and the telephoto end.

By making an arrangement such that a lower limit in conditionalexpression (16) is not surpassed, it becomes easy to suppress the loadof the zooming effect of the other lens units, and it becomes easy tocarry out the correction of various aberrations in a balanced manner. Bysuppressing the zooming load of the second lens unit, it becomes easy tosuppress the occurrence of various oblique aberrations such as thechromatic aberration of magnification and the curvature of field at thetelephoto end. By suppressing the zooming load of the third lens unit,it becomes easy to suppress the occurrence of the longitudinalaberration such as the spherical aberration at the telephoto end.

By making an arrangement such that an upper limit in conditionalexpression (16) is not surpassed, it becomes easy to suppress afluctuation in the aberration due to an increase in the zooming of thefourth lens unit. Moreover, when the fourth lens unit is let to be afocusing lens unit, it becomes easy to suppress a fluctuation in thecurvature of field at the time of focusing.

Regarding an air distance on an optical axis between the second lensunit and the third lens unit at the wide angle end for a focal length ofthe overall zoom lens system at the wide angle end, it is preferablethat the following conditional expression (17) is satisfied.

2.8<D _(2w) /f _(w)<4.2   (17)

3.5<(β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))<5.0   (9)

where,

D_(2w) denotes an air distance on an optical axis between the secondlens unit and the third lens unit at the wide angle end,

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end,

β_(2w) and β_(2t) denote a lateral magnification of the second lensunit, at the wide angle end and the telephoto end respectively,

β_(3w) and β_(3t) denote a lateral magnification of the third lens unit,at the wide angle end and the telephoto end respectively, and

β_(4w) and β_(4t) denote a lateral magnification of the fourth lensunit, at the wide angle end and the telephoto end respectively.

The description of conditional expression (9) will be omitted as it hasalready been described.

By making an arrangement such that a lower limit in conditionalexpression (17) is not surpassed, it is possible to secure an amount ofchange in a distance between the second lens unit and the third lensunit, and it is advantageous for securing the zooming ratio.

By satisfying conditional expression (9), and by making an arrangementsuch that an upper limit in conditional expression (17) is notsurpassed, the first lens unit and the second lens unit are broughtcloser to the third lens unit, and since it is possible to lower aheight of off-axis light rays, it is advantageous for making small alens diameter.

Regarding a preferable amount of movement of the third lens unit for thefocal length of the overall zoom lens system at the wide angle end, itis preferable that the following conditional expression (18) issatisfied.

1.3<Δ3G/f _(w)<2.4   (18)

where,

Δ3G denotes an amount of movement of the third lens unit from the wideangle end to the telephoto end, and

f_(w) denotes the focal length of the overall zoom lens system at thewide angle end.

By making an arrangement such that a lower limit in conditionalexpression (18) is not surpassed, even when the refracting power of thethird lens unit is suppressed, it becomes easy to secure the zoomingratio in the third lens unit, and it is advantageous for the aberrationcorrection.

By making an arrangement such that an upper limit in conditionalexpression (18) is not surpassed, the overall diameter of the zoom lenssystem at the telephoto end is suppressed, leading to small sizing inthe direction of thickness of the lens barrel.

Moreover, it is preferable that the zoom lens system according to thepresent invention includes an aperture stop which is disposedimmediately before the object side of the third lens unit, and that theaperture stop, at the time of zooming from the wide angle end to thetelephoto end, moves integrally with the third lens unit.

By disposing the aperture stop immediately before the object side of thethird lens unit which is involved importantly in an effect of imageformation, it is possible to make the size small in a radial directionwhile securing the refracting power of the third lens unit. Moreover,when such an arrangement is made, a change in a height of light rays atthe time of zooming in the third lens unit being small, a stable imageforming performance throughout the zoom range is achieved.

Moreover, it is preferable that the first lens unit includes one lenscomponent.

Similarly as in the second lens unit, in the first lens unit, a heightfrom a position on an optical axis of off-axis light rays increases.When the number of lens components in the first lens unit becomes large,the position of the exit pupil becomes far when seen from the objectside. Therefore, the height of the off-axis light rays in the first lensunit goes on becoming higher and higher, and a longitudinal thicknessfor securing an edge thickness is required to be more. Naturally, whenthe number of lenses increases, the longitudinal thickness of the firstlens unit becomes substantial. Therefore, forming the first lens unit byone lens component is advantageous for making the lens barrel compact.

The first lens unit may include a cemented lens component of a negativelens and a positive lens. When the first lens unit is let to be acemented lens, it is possible to carry out effectively the correction oflongitudinal chromatic aberration which becomes remarkable at the timeof making focus long at the telephoto end by making the zooming ratiohigh. Moreover, it is possible to suppress degradation of opticalperformance in relative decentering of the plurality of lenses due to anassembling error, and it is possible to contribute to an improvement inthe yield and lowering of cost.

Moreover, in a case of forming the first lens unit by one lenscomponent, it is preferable that conditional expressions (19) and (20)are satisfied.

0.725<IH/f _(w)<0.8   (19)

−1.0<D _(2w) /L _(11r)<1.0   (20)

where,

IH denotes the maximum light ray height of off-axis rays at an imageplane,

f_(w) denotes a focal length of the overall zoom lens system at the wideangle end,

D_(2w) denotes an air distance on an optical axis between the secondlens unit and the third lens unit at the wide angle end, and

L_(11r) denotes a radius of curvature of a surface nearest to the imageside of the first lens unit.

Conditional expression (19) is an expression which specifies apreferable ratio of an image height to a focal length at the wide angleend. It is the maximum value within a range which may be obtained when avalue of the image height changes.

By making an arrangement such that a lower limit in conditionalexpression (19) is not surpassed, it is advantageous for securing anangle of field at the wide angle end.

By making an arrangement such that an upper limit in conditionalexpression (19) is not surpassed, it is possible to suppress an increasein the number of lenses of the first lens unit and the second lens unitfor correction of an oblique aberration and securing an amount of light.

By making an arrangement such that a lower limit in conditionalexpression (20) is not surpassed, a surface on the image side of thefirst lens unit is not let to be a strong convex surface. Accordingly,it is advantageous for reduction of the oblique aberration near the wideangle end.

By making an arrangement such that an upper limit in conditionalexpression (20) is not surpassed, a surface on the image side of thefirst lens unit is not let to be a strong concave surface. Accordingly,it is advantageous for reduction of the longitudinal aberration near thetelephoto end.

Moreover, in the second lens unit, a difference in a height of off-axislight rays at the wide angle end and a height of off-axis light rays atthe telephoto end becomes substantial. Therefore, by disposing a lenshaving an aspheric surface in the second lens unit, an aberrationcorrection at the wide angle end and the telephoto end becomes easy.

Moreover, in the fourth lens unit, a difference in a height of off-axislight rays at the wide angle end and a height of off-axis light rays atthe telephoto end becomes substantial. Or, it is easy to separate alongitudinal light beam and an off-axis light beam.

Therefore, by disposing a lens having an aspheric surface in the fourthlens unit, an aberration correction at the wide angle end and thetelephoto end, and a correction of the curvature of field become easy.

At the time of zooming from the wide angle end to the telephoto end, itis preferable to move the first lens unit such that the first lens unitis on the object side at the telephoto end, than at the wide angle end.At this time, the first lens unit may be moved only toward the objectside, or may be moved toward the image side in a convex trajectory. Thesecond lens unit may be moved only toward the image side, or may bemoved toward the image side in a convex trajectory (locus).

It is preferable to move the third lens unit only toward the objectside. The fourth lens unit 4 may be moved only toward the object side,or may be moved toward the image side. Or, the fourth lens unit may bemoved toward the image side in a convex trajectory (locus).

Moreover, for cutting unnecessary light such as ghost and flare, a flareaperture apart from an aperture stop may be disposed. The flare aperturemay be disposed at any of locations namely, toward the object side ofthe first lens unit, or between the first lens unit and the second lensunit, or between the second lens unit and the third lens unit, andbetween the fourth lens unit and the image plane. An arrangement may bemade such that flare light rays are cut by a frame member, or anothermember may be arranged. Moreover, a direct painting, a direct coating,or sticking a seal on the optical system may be carried out. A shapethereof may be any shape such as an elliptical shape, a rectangularshape, a polygonal shape, and a range surrounded by a function curve.Moreover, not only a harmful light beam, but also a beam such as a comaflare around an image plane may be cut.

Moreover, the ghost and the flare may be reduced by applying anantireflection coating to each lens. A multi coating is desirable as itenables to reduce the ghost and the flare effectively. Moreover, aninfrared coating may be applied to lens surfaces and a cover glass etc.

Moreover, it is preferable to carry out focusing in the fourth lensunit. When the focusing is carried out in the fourth lens unit, a lensweight being light, and a load exerted on a motor is small. Furthermore,since the overall length does not change at the time of focusing and adrive motor can be disposed at an interior of a lens frame, it isadvantageous for making the lens frame compact.

The focusing in the fourth lens unit as described above is desirable.However, the focusing may be carried out in the first lens unit, thesecond lens unit, and the third lens unit. Moreover, the focusing may becarried out by drawing out the entire lens system toward the objectside. The focusing may be carried out by drawing out a part of the lensor by carrying over.

Moreover, there may be let to be an image pickup apparatus whichincludes a zoom lens system described in one of the abovementioneditems, and an image pickup element, which is disposed on an image sideof the zoom lens system, and which converts an image formed by the zoomlens system to an electric image.

Moreover, a shading of brightness around an image may be reduced byshifting a micro lens of the CCD. For instance, a design of the microlens of the CCD may be changed according to an angle of incidence oflight rays at each image height. Moreover, a degradation amount aroundthe image may be corrected by image processing.

Moreover, a distortion may be corrected by carrying out image processingelectrically after taking a picture, upon causing distortionintentionally in the optical system.

Moreover, letting the zoom lens system to be a four-unit zoom lenssystem is advantageous for further small sizing. An arrangement may bemade such that the astigmatism is corrected even more favorably bydisposing an aspheric lens having a small refracting power, immediatelybefore an image pickup surface.

Moreover, it is preferable that a plurality of the abovementionedarrangements and conditional expressions are satisfied simultaneously.

Regarding the conditional expressions, when the upper limit value andthe lower limit value are restricted as described below, further effectcan be assured.

Only the lower limit value or only the upper limit value in theconditional expressions may be restricted.

It is more preferable to let conditional expression (1) be as follows.

−0.85<SF _(3n)<−0.25   (1′)

It is even more preferable to let conditional expression (1) be asfollows.

−0.80<SF _(3n)<−0.5   (1″)

It is more preferable to let conditional expression (2) be as follows.

55<νd₃<115   (2′)

It is even more preferable to let conditional expression (2) be asfollows.

60<νd₃<112   (2″)

It is more preferable to let conditional expression (3) be as follows.

0.09<D ₃ /f ₃<0.18   (3′)

It is even more preferable to let conditional expression (3) be asfollows.

0.09<D ₃ /f ₃<0.15   (3″)

It is more preferable to let conditional expression (5) be as follows.

0.26<UY _(3G) /f ₃<0.45   (5′)

It is even more preferable to let conditional expression (5) be asfollows.

0.27<UY _(3G) /f ₃<0.40   (5″)

It is more preferable to let conditional expression (6) be as follows.

0.65<UY _(3G) /f _(w)<0.95   (6′)

It is even more preferable to let conditional expression (6) be asfollows.

0.70<UY _(3G) /f _(w)<0.90   (6″)

It is more preferable to let conditional expression (7) be as follows.

7.5<f ₁ /f _(w)<9.5   (7′)

It is even more preferable to let conditional expression (7) be asfollows.

8.0<f ₁ /f _(w)<9.2   (7″)

It is more preferable to let conditional expression (8) be as follows.

1.65<|f ₂ /f _(w)|<2.05   (8′)

It is even more preferable to let conditional expression (8) be asfollows.

1.70<|f ₂ /f _(w)<2.00   (8″)

It is more preferable to let conditional expression (10) be as follows.

2.2<f ₃ /f _(w)<2.9   (10′)

It is even more preferable to let conditional expression (10) be asfollows.

2.4<f ₃ /f _(w)<2.8   (10″)

It is more preferable to let conditional expression (11) be as follows.

3.6<f ₄ /f _(w)<5.25   (11′)

It is even more preferable to let conditional expression (11) be asfollows.

3.8<f ₄ /f _(w)<5.00   (11″)

It is more preferable to let conditional expression (12) be as follows.

9.2<L _(w) /f _(w)<10.0   (12′)

It is even more preferable to let conditional expression (12) be asfollows.

9.4<L _(w) /f _(w)<9.8   (12″)

It is more preferable to let conditional expression (13) be as follows.

0.55<(β_(2t)/β_(2w))/(β_(3t)/β_(3w))<0.95   (13′)

It is even more preferable to let conditional expression (13) be asfollows.

0.60<(β_(2t)/β_(2w))/(β_(3t)/β_(3w))<0.90   (13″)

It is more preferable to let conditional expression (14) be as follows.

1.5<β_(2t)/β_(2w)<2.0   (14′)

It is even more preferable to let conditional expression (14) be asfollows.

1.6<β_(2t)/β_(2w)<1.9   (14″)

It is more preferable to let conditional expression (15) be as follows.

1.9<β_(3t)/β_(3w)<2.8   (15′)

It is even more preferable to let conditional expression (15) be asfollows.

2.0<β_(3t)/β_(3w)<2.7   (15″)

It is more preferable to let conditional expression (16) be as follows.

0.7<β_(4t)/β_(4w)<1.2   (16′)

It is even more preferable to let conditional expression (16) be asfollows.

0.8<β_(4t)/β_(4w)<1.1   (16″)

It is more preferable to let conditional expression (17) be as follows.

3.0<D _(2w) /f _(w)<4.0   (17′)

It is even more preferable to let conditional expression (17) be asfollows.

3.2<D _(2w) /f _(w)<3.8   (17″)

It is more preferable to let conditional expression (18) be as follows.

1.4<Δ3G/f _(w)<2.3   (18′)

It is even more preferable to let conditional expression (18) be asfollows.

1.5<Δ3G/f _(w)<2.2   (18″)

It is more preferable to let conditional expression (20) be as follows.

−0.8<D _(2w) /L _(11r)<0.8   (20′)

It is even more preferable to let conditional expression (20) be asfollows.

−0.5<D _(2w) /L _(11r)<0.5   (20″)

Exemplary embodiments of the zoom lens system and the image pickupapparatus according to the present invention will be described below indetail. However, the present invention is not restricted to theembodiments described below.

Each of the embodiments is a zoom lens system having a high imageforming performance with a brightness having the F value of about 1.8 atthe wide angle end, a wide angle of field of about 75° at the wide angleend, and a zooming ratio of about four times, which is suitable forslimming when a lens barrel is collapsed, and which is compact.Moreover, it is a low-price zoom lens system in which, an exit pupil canbe easily moved away from an image plane, and which is suitable for animage pickup element such as a CCD and a CMOS.

Moreover, focusing from a long-distance object to a short-distance iscarried out by drawing out the fourth lens unit toward the object side.

When not in use, an optical axis of the third lens unit may be separatedfrom an optical axis of the other lens units by moving parallel to adirection of short side of an image pickup surface, and may beaccommodated in a collapsed state to be positioned at a lower side (orat an upper side) of the fourth lens unit.

A lower side (or an upper side) of the lenses forming the fourth lensunit may subjected to D-cut parallel to a longitudinal direction of theimage pickup surface.

Moreover, a thirteenth surface in numerical data is a virtual surface.

Furthermore, two parallel plates are a low pass filter on which aninfrared-cutting coat is applied, and a transparent cover member whichis positioned at a front surface of the image pickup surface of theimage pickup element.

Moreover, the last surface in the diagrams is an image surface, atwhich, the image pickup surface of the image pickup element ispositioned.

By installing such zoom lens system in an image pickup apparatus such asa digital camera, the image pickup apparatus becomes an image pickupapparatus having an improved performance.

A zoom lens system according to a first embodiment, as shown in FIG. 1A,FIG. 1B, and FIG. 1C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and anintermediate focal length state, moves toward object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the object side. Thesecond lens unit G2 is positioned on the image side at the telephotoend, than at the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a biconvex positive lens.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the object side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving a convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to a second embodiment, as shown in FIG.2A, FIG. 2B, and FIG. 2C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and anintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement at the intermediate focal lengthstate, moves toward the object side. The second lens unit G2 ispositioned on the image side at the telephoto end, than at the wideangle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens made of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a biconvex positive lens.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected on the object side, and a cemented lens of a biconcave negativelens and a biconvex positive lens.

The fourth lens unit G4 includes a cemented lens of a biconvex positivelens and a biconcave negative lens.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the object side in the third lensunit G3, and a surface on the object side of the biconvex positive lensin the fourth lens unit G4.

A zoom lens system according to a third embodiment, as shown in FIG. 3A,FIG. 3B, and FIG. 3C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and anintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement at the intermediate focal lengthstate, moves toward the object side. The second lens unit G2 ispositioned on the image side at the telephoto end, than at the wideangle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens made of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a positive meniscus lens having a convex surface directedtoward the object side.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to a fourth embodiment, as shown in FIG.4A, FIG. 4B, and FIG. 4C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and anintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement at the intermediate focal lengthstate, moves toward the object side. The second lens unit G2 ispositioned on the image side at the telephoto end, than at the wideangle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a negative meniscus lens having a convex surface directedtoward the object side.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to a fifth embodiment, as shown in FIG. 5A,FIG. 5B, and FIG. 5C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and theintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the object side. Thesecond lens unit G2 is positioned on the image side at the telephotoend, than at the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a positive meniscus lens having a convex surface directedtoward the object side.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to a sixth embodiment, as shown in FIG. 6A,FIG. 6B, and FIG. 6C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and theintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the object side. Thesecond lens unit G2 is positioned on the image side at the telephotoend, than at the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a biconvex positive lens.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to a seventh embodiment, as shown in FIG.7A, FIG. 7B, and FIG. 7C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and theintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the object side. Thesecond lens unit G2 is positioned on the image side at the telephotoend, than at the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the image side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a biconvex positive lens.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side.

A zoom lens system according to an eighth embodiment, as shown in FIG.8A, FIG. 8B, and FIG. 8C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and theintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting a direction of movement between the intermediate focal lengthstate and the telephoto end, moves toward the object side. The secondlens unit G2 is positioned on the image side at the telephoto end, thanat the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the object side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a negative meniscus lenshaving a convex surface directed toward the object side, and a positivemeniscus lens having a convex surface directed toward the object side.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a negativemeniscus lens having a convex surface directed toward the image side anda positive meniscus lens having a convex surface directed toward theimage side.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is provided to six surfaces namely, both surfaces ofthe negative meniscus lens having the convex surface directed toward theobject side in the second lens unit G2, both surfaces of the biconvexpositive lens on the object side and a surface on the image side of thepositive meniscus lens having the convex surface directed toward theimage side in the third lens unit G3, and a surface on the object sideof the positive meniscus lens having the convex surface directed towardthe object side in the fourth lens unit G4.

A zoom lens system according to a ninth embodiment, as shown in FIG. 9A,FIG. 9B, and FIG. 9C, includes in order from an object side, a firstlens unit G1 having a positive refracting power, a second lens unit G2having a negative refracting power, an aperture stop S, a third lensunit G3 having a positive refracting power, and a fourth lens unit G4having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end to theintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting a direction of movement between the intermediate focal lengthstate and the telephoto end, moves toward the object side. The secondlens unit G2 is positioned on the image side at the telephoto end, thanat the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting the direction of movement between the intermediate focallength state and the telephoto end, moves toward the object side. Thefourth lens unit G4 is positioned on the object side at the telephotoend, than at the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a biconvex positive lens.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconcave positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to a tenth embodiment, as shown in FIG.10A, FIG. 10B, and FIG. 10C, includes in order from an object side, afirst lens unit G1 having a positive refracting power, a second lensunit G2 having a negative refracting power, an aperture stop S, a thirdlens unit G3 having a positive refracting power, and a fourth lens unitG4 having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and theintermediate focal length state, moves toward the object side. The firstlens unit G1 is positioned on the object side at the telephoto end, thanat the wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting a direction of movement between the intermediate focal lengthstate and the telephoto end, moves toward the object side. The secondlens unit G2 is positioned on the image side at the telephoto end, thanat the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting a direction of movement between the intermediate focal lengthstate and the telephoto end, moves toward the object side. The fourthlens unit G4 is positioned on the object side at the telephoto end, thanat the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a biconcave negativelens, and a biconvex positive lens.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a negative meniscus lens having a convex surfacedirected toward the object side, and a cemented lens of a biconcavenegative lens and a biconvex positive lens.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely, both surfaces ofthe biconcave negative lens in the second lens unit G2, both surfaces ofthe biconvex positive lens on the object side and a surface on the imageside of the biconvex positive lens on the image side in the third lensunit G3, and a surface on the object side of the positive meniscus lenshaving the convex surface directed toward the object side in the fourthlens unit G4.

A zoom lens system according to an eleventh embodiment, as shown in FIG.11A, FIG. 11B, and FIG. 11C, includes in order from an object side, afirst lens unit G1 having a positive refracting power, a second lensunit G2 having a negative refracting power, an aperture stop S, a thirdlens unit G3 having a positive refracting power, and a fourth lens unitG4 having a positive refracting power.

At the time of zooming from the wide angle end to the telephoto end, thefirst lens unit G1, first moves toward the image side, and uponinverting a direction of movement between the wide angle end and theintermediate focal length state, moves toward the object side. The firstlens unit is positioned on the object side at the telephoto end, than atthe wide angle end.

The second lens unit G2, first moves toward the image side, and uponinverting a direction of movement between the intermediate focal lengthstate and the telephoto end, moves toward the object side. The secondlens unit G2 is positioned on the image side at the telephoto end, thanat the wide angle end.

The third lens unit G3 moves only toward the object side.

The fourth lens unit G4, first moves toward the object side, and uponinverting a direction of movement between the intermediate focal lengthstate and the telephoto end, moves toward the object side. The fourthlens unit G4 is positioned on the object side at the telephoto end, thanat the wide angle end.

In order from the object side, the first lens unit G1 includes acemented lens of a negative meniscus lens having a convex surfacedirected toward the object side and a positive meniscus lens having aconvex surface directed toward the object side.

The second lens unit G2 includes a negative meniscus lens having aconvex surface directed toward the object side, a negative meniscus lenshaving a convex surface directed toward the object side, and a positivemeniscus lens having a convex surface directed toward the object side.

The third lens unit G3 includes a biconvex positive lens, a cementedlens of a positive meniscus lens having a convex surface directed towardthe object side and a biconcave negative lens, and a cemented lens of anegative meniscus lens having a convex surface directed toward the imageside and a positive meniscus lens having a convex surface directedtoward the image side.

The fourth lens unit G4 includes a positive meniscus lens having aconvex surface directed toward the object side.

An aspheric surface is used for six surfaces namely both surfaces of thenegative meniscus lens having the convex surface directed toward theobject side in the second lens unit G2, both surfaces of the biconvexpositive lens on the object side and a surface on the image side of thepositive meniscus lens having the convex surface directed toward theimage side in the third lens unit G3, and a surface on the object sideof the positive meniscus lens having the convex surface directed towardthe object side in the fourth lens unit G4.

Numerical data of each embodiment described above is shown below. Apartfrom symbols described above, f denotes a focal length of the entirezoom lens system, F_(NO) denotes an F number, ω denotes a half angle offield, WE denotes a wide angle end, ST denotes an intermediate state, TEdenotes a telephoto end, each of r denotes radius of curvature of eachlens surface, each of d denotes a distance between two lenses, each ofnd denotes a refractive index of each lens for a d-line, and each of vddenotes an Abbe' s number for each lens. Further, * denotes an asphericdata, S denotes a stop.

BF (back focus) is a unit which is expressed upon air conversion of adistance from the last lens surface up to a paraxial image plane.

When x is let to be an optical axis with a direction of traveling oflight as a positive (direction), and y is let to be in a directionorthogonal to the optical axis, a shape of the aspheric surface isdescribed by the following expression.

x=(y ² /r)/[1+{1−(K+1)(y/r)²}^(1/2) ]+A ₄ y ⁴ y ⁴ +A ₆ u ⁶ +A ₈ y ⁸ +A₁₀ y ¹⁰ +A ₁₂ y ¹²

where, r denotes a paraxial radius of curvature, K denotes a conicalcoefficient, A4, A6, A8, A10, and A₁₂ denote aspherical surfacecoefficients of a fourth order, a sixth order, an eight order, a tenthorder, and a twelfth order respectively. Moreover, in the asphericalsurface coefficients, ‘e-n’ (where, n is an integral number) indicates‘10^(−n)’.

Zoom data of each embodiment are values in a state in which, an objectat an infinite object point is focused.

From left, zoom data are values at the wide angle end WE, theintermediate focal length state ST1, the telephoto end TE, a state ST2between the wide angle end and the intermediate focal length state, astate ST3 between the intermediate focal length state and the telephotoend.

Moreover, aberration diagrams show aberrations at the wide angle end,the intermediate focal length state, and the telephoto end.

Numerical Example 1 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 32.407 1.001.94595 17.98  2 24.711 3.71 1.81600 46.62  3 181.957 Variable  4 62.5351.00 1.88300 40.76  5 8.539 4.99  6* −35.795 0.80 1.58313 59.38  7*15.195 1.40  8 23.234 2.08 2.00069 25.46  9 −202.836 Variable 10 (Stop)∞ 0.50 11* 11.020 2.44 1.58313 59.38 12* −53.044 0.00 13 ∞ 0.10 14 9.1832.40 1.80100 34.97 15 17.413 0.70 1.80518 25.42 16 6.265 1.80 17 −40.8990.70 1.69895 30.13 18 12.775 2.64 1.49700 81.61 19* −10.249 Variable 20*12.126 2.49 1.49700 81.54 21 63.255 Variable 22 ∞ 0.50 1.54771 62.84 23∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.01 Image plane ∞ (Light receivingsurface) Aspherical surface data 6th surface k = 0.000 A4 = 8.82324e−05,A6 = −3.16588e−06, A8 = 3.95523e−08, A10 = −3.06841e−10 7th surface k =0.000 A4 = −2.34654e−05, A6 = −3.40520e−06, A8 = 3.18367e−08, A10 =−1.86747e−10 11th surface k = 0.000 A4 = −5.09661e−05, A6 =−4.13815e−08, A8 = −5.03716e−09, 12th surface k = 0.000 A4 =1.14214e−04, A6 = 8.07123e−08 19th surface k = 0.000 A4 = −8.26476e−06,A63.14592e−07=, A8 = −8.73717e−08 20th surface k = 0.000 A4 =−2.99323e−05, A6 = 2.94977e−08 Zoom data (∞) WE ST1 TE ST2 ST3 Focallength 6.06 12.72 23.50 8.22 18.76 Fno. 1.85 2.19 2.54 1.97 2.39 Angleof field 2ω 78.41 39.96 21.95 59.83 27.50 fb (in air) 7.33 8.97 8.278.10 9.19 Total length (in air) 60.49 57.99 65.85 57.26 62.17 d3 0.307.62 16.02 2.82 12.89 d9 21.11 6.50 1.10 13.63 2.44 d19 3.00 6.15 11.723.96 8.90 d21 5.17 6.82 6.10 5.94 7.03 Unit focal length f1 = 50.47 f2 =−11.67 f3 = 16.15 f4 = 29.71

Numerical Example 2 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 34.234 1.001.94595 17.98  2 26.431 3.40 1.81600 46.62  3 304.697 Variable  4 58.7421.00 1.88300 40.76  5 8.027 4.28  6* −37.316 1.00 1.69350 53.21  7*27.854 1.53  8 25.275 1.91 1.92286 20.88  9 −1287.866 Variable 10 (Stop)∞ 0.50 11* 14.062 2.11 1.85135 40.10 12* −229.434 0.01 13 ∞ 0.16 148.396 2.43 1.58913 61.14 15 25.547 0.70 1.74077 27.79 16 6.543 1.66 17−45.415 0.70 1.76182 26.52 18 13.788 2.50 1.58313 59.38 19* −12.682Variable 20* 14.086 3.00 1.74320 49.34 21 −61.445 0.80 1.69895 30.13 2250.317 Variable 23 ∞ 0.50 1.54771 62.84 24 ∞ 0.50 25 ∞ 0.50 1.5163364.14 26 ∞ 1.02 Image plane ∞ (Light receiving surface) Asphericalsurface data 6th surface k = 0.000 A4 = 1.22305e−04, A6 = −3.78786e−06,A8 = 1.63670e−08, A10 = −3.83663e−10 7th surface k = 0.000 A4 =4.70833e−05, A6 = −3.49825e−06, A8 = −1.99464e−08, A10 = 2.89545e−1011th surface k = −0.862 A4 = 5.16574e−05, A6 = 1.85386e−07, 12th surfacek = 0.000 A4 = 9.42257e−05 19th surface k = 0.000 A4 = 1.62253e−05, A6 =1.15227e−07 20th surface k = 0.000 A4 = −5.48767e−06 Zoom data (∞) WEST1 TE ST2 ST3 Focal length 6.06 12.73 23.49 8.18 18.78 Fno. 1.88 2.232.71 2.00 2.51 Angle of field 2ω 78.00 39.61 21.84 59.63 27.44 fb (inair) 5.41 7.35 7.15 6.33 8.09 Total length (in air) 59.89 59.47 68.5057.53 63.90 d3 0.48 7.72 14.78 2.99 11.70 d9 19.49 6.24 1.19 12.74 2.09d19 5.81 9.46 16.68 6.78 13.34 d22 3.23 5.18 4.97 4.16 5.91 Unit focallength f1 = 49.36 f2 = −10.76 f3 = 15.93 f4 = 24.31

Numerical Example 3 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 37.516 1.001.94595 17.98  2 28.269 3.65 1.81600 46.62  3 308.051 Variable  4 85.0411.00 1.88300 40.76  5 8.923 4.16  6* −199.432 1.00 1.59201 67.02  7*14.964 2.30  8 20.381 2.02 1.92286 20.88  9 76.402 Variable 10 (Stop) ∞0.50 11* 13.680 2.11 1.85135 40.10 12* −448.191 0.00 13 ∞ 0.10 14 8.4722.34 1.65160 58.55 15 25.860 0.70 1.74077 27.79 16 6.299 1.87 17 −39.8090.70 1.78472 25.68 18 15.491 2.60 1.58313 59.38 19* −12.041 Variable 20*11.431 2.80 1.49700 81.54 21 83.333 Variable 22 ∞ 0.50 1.54771 62.84 23∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.02 Image plane ∞ (Light receivingsurface) Aspherical surface data 6th surface k = 0.000 A4 = 1.83861e−04,A6 = −4.87899e−06, A8 = 5.56765e−08, A10 = −4.48996e−10 6th surface 7thsurface k = 0.000 A4 = 8.73933e−05, A6 = −5.31729e−06, A8 = 3.79977e−08,A10 = −2.41882e−10 11th surface k = 0.000 A4 = 2.06870e−05, A6 =1.06760e−07 12th surface k = 0.000 A4 = 1.05879e−04 19th surface k =0.000 A4 = 2.54312e−05, A6 = 2.25398e−08 20th surface k = 0.000 A4 =−2.05812e−05 Zoom data (∞) WE ST1 TE ST2 ST3 Focal length 6.06 12.7323.49 8.18 18.79 Fno. 1.88 2.24 2.70 2.00 2.52 Angle of field 2ω 77.9939.78 21.84 59.61 27.53 fb (in air) 5.67 7.66 7.18 6.59 8.33 Totallength (in air) 61.42 60.78 70.68 59.16 65.58 d3 0.73 8.38 16.98 3.5912.88 d9 20.29 6.35 1.47 13.32 2.16 d19 5.89 9.55 16.20 6.82 13.36 d213.50 5.48 5.00 4.42 6.16 Unit focal length f1 = 55.03 f2 = −11.03 f3 =15.85 f4 = 26.32

Numerical Example 4 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 37.599 1.001.94595 17.98  2 28.758 3.40 1.81600 46.62  3 326.912 Variable  4 69.5951.00 1.88300 40.76  5 8.468 4.32  6* −55.584 0.80 1.58313 59.38  7*20.238 2.05  8 23.491 1.57 1.92286 20.88  9 143.909 Variable 10 (Stop) ∞0.50 11* 14.093 2.09 1.85135 40.10 12* −220.843 0.00 13 ∞ 0.10 14 8.1872.38 1.65160 58.55 15 20.827 0.60 1.75520 27.51 16 6.246 1.89 17 −35.7120.60 1.74077 27.79 18 12.006 2.60 1.58313 59.38 19* −11.961 Variable 20*11.612 2.80 1.49700 81.54 21 90.909 Variable 22 ∞ 0.50 1.54771 62.84 23∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.02 Image plane ∞ (Light receivingsurface) Aspherical surface data 6th surface k = 0.000 A4 = 1.65903e−04,A6 = −4.84257e−06, A8 = 3.83218e−08, A10 = −3.82278e−10 7th surface k =0.000 A4 = 7.51457e−05, A6 = −4.81271e−06, A8 = 6.36274e−09, A10 =9.70635e−11 11th surface k = 0.000 A4 = 1.63367e−05, A6 = 7.98464e−0812th surface k = 0.000 A4 = 9.89562e−05 19th surface k = 0.000 A4 =2.58997e−05, A6 = −2.09003e−07 20th surface k = 0.000 A4 = −1.87694e−05Zoom data (∞) WE ST1 TE ST2 ST3 Focal length 6.06 12.75 23.49 8.21 18.78Fno. 1.85 2.21 2.66 1.97 2.47 Angle of field 2ω 77.99 39.72 21.84 59.3827.46 fb (in air) 5.65 7.65 7.20 6.55 8.21 Total length (in air) 60.0359.08 68.76 57.73 64.04 d3 0.81 8.28 16.74 3.67 13.13 d9 20.18 6.19 1.2813.18 2.20 d19 5.69 9.27 15.85 6.64 12.81 d21 3.48 5.48 5.03 4.38 6.03Unit focal length f1 = 54.55 f2 = −11.10 f3 = 15.67 f4 = 26.48

Numerical Example 5 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 32.479 1.001.94595 17.98  2 24.920 3.63 1.81600 46.62  3 181.444 Variable  4 82.1261.00 1.88300 40.76  5 8.608 3.75  6* −461.718 0.80 1.58313 59.38  7*14.319 2.80  8 25.709 1.61 1.92286 20.88  9 444.290 Variable 10 (Stop) ∞0.50 11* 11.650 2.65 1.74320 49.34 12* −64.594 0.00 13 ∞ 0.10 14 7.5352.52 1.49700 81.54 15 18.245 0.60 1.75520 27.51 16 5.784 2.09 17 −26.9610.59 1.84666 23.78 18 75.476 1.92 1.49700 81.54 19* −10.082 Variable 20*12.332 2.30 1.58313 59.38 21 49.198 Variable 22 ∞ 0.50 1.54771 62.84 23∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.00 Image plane ∞ (Light receivingsurface) Aspherical surface data 6th surface k = 0.000 A4 =−1.34305e−04, A6 = −3.35475e−08, A8 = 2.12158e−08, A10 = −3.98495e−107th surface k = 0.000 A4 = −2.72863e−04, A6 = 1.41606e−08, A8 =7.26216e−09, A10 = −2.57845e−10 11th surface k = 0.000 A4 =−2.26557e−05, A6 = 3.87409e−08 12th surface k = 0.000 A4 = 1.03062e−0419th surface k = 0.000 A4 = 1.10738e−04, A6 = 1.58748e−07 20th surface k= 0.000 A4 = 4.43250e−06, A6 = 1.78804e−07 Zoom data (∞) WE ST1 TE ST2ST3 Focal length 6.05 12.70 23.48 8.21 18.74 Fno. 1.85 2.20 2.64 1.962.45 Angle of field 2ω 77.99 39.80 21.74 59.43 27.44 fb (in air) 5.817.65 6.15 6.84 7.71 Total length (in air) 60.06 57.43 65.90 56.75 61.72d3 0.85 7.94 16.10 3.52 12.82 d9 21.10 6.57 1.91 13.58 2.68 d19 4.437.40 13.88 4.94 10.64 d21 3.66 5.50 3.99 4.69 5.56 Unit focal length f1= 50.57 f2 = −11.30 f3 = 15.49 f4 = 27.59

Numerical Example 6 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 32.304 1.001.94595 17.98  2 24.943 3.64 1.81600 46.62  3 172.655 Variable  4 71.0021.00 1.88300 40.76  5 8.475 4.64  6* −53.111 0.80 1.58313 59.38  7*14.386 1.69  8 26.088 1.95 2.00069 25.46  9 −134.426 Variable 10 (Stop)∞ 0.50 11* 13.456 2.07 1.85135 40.10 12* −118.344 0.00 13 ∞ 0.10 147.116 2.48 1.49700 81.54 15 17.554 0.60 1.80518 25.42 16 5.880 1.75 17−29.806 0.60 1.75520 27.51 18 19.475 2.65 1.58313 59.38 19* −11.467Variable 20* 11.705 2.67 1.49700 81.54 21 129.496 Variable 22 ∞ 0.501.54771 62.84 23 ∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.02 Image plane ∞(Light receiving surface) Aspherical surface data 6th surface k = 0.000A4−1.28981e−04=, A6 = 2.69614e−06, A8 = −4.77413e−08, A10 = 1.62318e−107h surface k = 0.000 A4 = −2.71603e−04, A6 = 2.76804e−06, A8 =−6.52305e−08, A10 = 3.78272e−10 11th surface k = 0.000 A4 = 7.65870e−06,A6 = −4.40696e−07, A8 = −3.41785e−09 12th surface k = 0.000 A4 =9.62632e−05, A6 = −6.84479e−07 19th surface k = 0.000 A4 = 3.81210e−05,A6 = 2.22804e−07, A8 = −2.27952e−08 20th surface k = 0.000 A4 =−1.04608e−05, A6 = 4.43120e−08 Zoom data (∞) WE ST1 TE ST2 ST3 Focallength 6.07 12.73 23.52 8.23 18.79 Fno. 1.85 2.16 2.59 1.95 2.39 Angleof field 2ω 77.96 39.90 21.81 59.40 27.49 fb (in air) 5.84 7.68 6.446.73 7.81 Total length (in air) 60.37 57.46 65.71 57.26 61.62 d3 0.467.90 15.96 3.38 12.87 d9 21.11 6.06 1.08 13.53 1.98 d19 4.84 7.68 14.105.48 10.83 d21 3.67 5.51 4.26 4.56 5.64 Unit focal length f1 = 50.70 f2= −11.72 f3 = 15.94 f4 = 25.70

Numerical Example 7 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 32.493 1.001.94595 17.98  2 24.819 3.71 1.81600 46.62  3 183.549 Variable  4 63.2821.00 1.88300 40.76  5 8.498 5.04  6* −36.519 0.80 1.58313 59.38  7*15.608 1.32  8 23.651 2.08 2.00069 25.46  9 −188.878 Variable 10 (Stop)∞ 0.50 11* 11.952 2.24 1.69350 53.21 12* −84.433 0.00 13 ∞ 0.10 14 9.5602.44 1.77250 49.60 15 17.376 0.70 1.74000 28.30 16 6.253 1.97 17 −40.0300.70 1.69895 30.13 18 12.750 2.61 1.49700 81.61 19* −10.553 Variable 20*11.804 2.55 1.49700 81.54 21 71.445 Variable 22 ∞ 0.50 1.54771 62.84 23∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.03 Image plane ∞ (Light receivingsurface) Aspherical surface data 6th surface k = 0.000 A4 = 3.88874e−05,A6 = −1.28328e−06, A8 = 3.13845e−09, A10 = −8.86196e−11 7th surface k =0.000 A4 = −7.29768e−05, A6 = −1.42649e−06, A8 = −9.39329e−09, A10 =1.05903e−10 11th surface k = 0.000 A4 = −2.87417e−05, A6 = −3.33033e−07,A8 = −3.40624e−09 12th surface k = 0.000 A4 = 9.32699e−05, A6 =−2.78366e−07 19th surface k = 0.000 A4 = 7.48009e−06, A6 = 1.98580e−07,A8 = −8.10780e−08 20th surface k = 0.000 A4 = −2.49722e−05, A6 =−7.43539e−09 Zoom data (∞) WE ST1 TE ST2 ST3 Focal length 6.07 12.7323.52 8.24 18.77 Fno. 1.85 2.18 2.54 1.97 2.38 Angle of field 2ω 78.4640.01 21.91 59.80 27.51 fb (in air) 6.52 8.31 7.47 7.27 8.49 Totallength (in air) 60.45 57.63 65.64 57.23 61.93 d3 0.30 7.57 16.03 2.8312.94 d9 21.11 6.31 1.09 13.62 2.35 d19 3.77 6.69 12.30 4.76 9.41 d214.34 6.13 5.29 5.08 6.31 Unit focal length f1 = 50.52 f2 = −11.66 f3 =15.93 f4 = 28.05

Numerical Example 8 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 32.650 1.001.94595 17.98  2 25.397 3.62 1.81600 46.62  3 179.536 Variable  4 69.4501.00 1.88300 40.76  5 8.584 3.91  6* 151.215 0.80 1.58313 59.38  7*13.194 2.66  8 25.436 1.65 1.92286 20.88  9 272.152 Variable 10 (Stop) ∞0.50 11* 13.592 2.27 1.74320 49.34 12* −48.258 0.00 13 ∞ 0.10 14 6.8602.68 1.49700 81.54 15 17.551 0.59 1.75520 27.51 16 5.593 1.95 17 −20.0660.60 1.92286 20.88 18 −80.822 2.00 1.58313 59.38 19* −10.406 Variable20* 11.944 2.62 1.49700 81.54 21 84.174 Variable 22 ∞ 0.50 1.54771 62.8423 ∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.02 Image plane ∞ (Lightreceiving surface) Aspherical surface data 6th surface k = 0.000 A4 =−4.47230e−04, A6 = 1.02657e−05, A8 = −1.53720e−07, A10 = 7.29943e−10 7thsurface k = 0.000 A4 = −6.03831e−04, A6 = 1.14883e−05, A8 =−2.01411e−07, A10 = 1.19791e−09 11th surface k = 0.000 A4 =−1.43577e−05, A6 = −5.53403e−07, A8 = −8.85897e−09 12th surface k =0.000 A4 = 8.95102e−05, A6 = −1.03207e−06 19th surface k = 0.000 A4 =8.70021e−05, A6 = 3.84489e−07, A8 = −1.40489e−08 20th surface k = 0.000A4 = −2.65103e−06, A6 = 1.62547e−07 Zoom data (∞) WE ST1 TE ST2 ST3Focal length 6.07 12.74 23.52 8.22 18.78 Fno. 1.85 2.18 2.61 1.96 2.43Angle of field 2ω 77.96 39.69 21.78 59.32 27.42 fb (in air) 5.69 7.686.44 6.64 7.85 Total length (in air) 59.96 57.05 65.23 56.76 61.05 D30.63 7.89 15.90 3.36 12.57 D9 21.10 6.33 1.39 13.62 2.26 D19 4.58 7.1913.55 5.18 10.42 D21 3.51 5.51 4.26 4.47 5.68 Unit focal length f1 =50.84 f2 = −11.43 f3 = 15.48 f4 = 27.67

Numerical Example 9 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 31.634 1.001.94595 17.98  2 24.337 3.70 1.81600 46.62  3 169.931 Variable  4 71.4001.00 1.88300 40.76  5 8.713 4.86  6* −49.021 0.80 1.58313 59.38  7*13.893 1.48  8 22.967 2.10 2.00069 25.46  9 −221.415 Variable 10 (Stop)∞ 0.50 11* 12.253 2.10 1.74320 49.34 12* −277.973 0.00 13 ∞ 0.10 148.188 2.34 1.64000 60.08 15 17.842 0.70 1.74000 28.30 16 6.012 2.18 17−38.264 0.70 1.72825 28.46 18 12.558 2.56 1.58313 59.38 19* −12.311Variable 20* 11.747 2.67 1.49700 81.54 21 95.158 Variable 22 ∞ 0.501.54771 62.84 23 ∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 0.97 Image plane ∞(Light receiving surface) Aspherical surface data 6th surface k− = 0.000A4 = 1.25719e−05, A6 = −1.15184e−06, A8 = 1.25233e−08, A10 =−1.37009e−10 7th surface k = 0.000 A4 = −1.19585e−04, A6 = −1.40665e−06,A8 = 5.70135e−09, A10 = −5.59580e−11 11th surface k = 0.000 A4 =5.20165e−06, A6 = −4.97308e−07, A8 = −2.78846e−09 12th surface k = 0.000A4 = 1.03347e−04, A6 = −6.49250e−07 19th surface k = 0.000 A4 =3.38150e−05, A6 = −4.08974e−07, A8 = 9.72395e−10 20th surface k = 0.000A4 = −2.09352e−05, A6 = 5.82527e−08 Zoom data (∞) WE ST1 TE ST2 ST3Focal length 6.05 12.70 23.47 8.22 18.74 Fno. 1.85 2.18 2.56 1.97 2.38Angle of field 2ω 78.42 40.23 21.95 59.92 27.65 fb (in air) 6.65 8.196.85 7.35 8.18 Total length (in air) 60.21 56.86 65.13 56.77 61.17 d30.30 7.24 15.77 2.81 12.60 d9 21.11 5.99 1.08 13.46 2.06 d19 3.36 6.6612.64 4.37 9.55 d21 4.53 6.06 4.73 5.22 6.06 Unit focal length f1 =49.61 f2 = −11.93 f3 = 16.15 f4 = 26.68

Numerical Example 10 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 31.866 1.001.94595 17.98  2 24.559 3.71 1.81600 46.62  3 174.804 Variable  4 60.0471.00 1.88300 40.76  5 8.506 5.02  6* −37.235 0.80 1.58313 59.38  7*14.856 1.33  8 23.081 2.10 2.00069 25.46  9 −193.679 Variable 10 (Stop)∞ 0.50 11* 12.728 2.10 1.74320 49.34 12* −166.062 0.00 13 ∞ 0.10 148.533 2.26 1.64000 60.08 15 18.398 0.70 1.72825 28.46 16 6.251 2.21 17−39.806 0.70 1.68893 31.07 18 14.820 2.58 1.49700 81.54 19* −10.625Variable 20* 11.681 2.50 1.49700 81.61 21 65.043 Variable 22 ∞ 0.501.54771 62.84 23 ∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.01 Image plane ∞(Light receiving surface) Aspherical surface data 6th surface k = 0.000A4 = 1.39775e−05, A6 = −5.89083e−07, A8 = −3.00001e−09, A10 =−4.86913e−11 7th surface k = 0.000 A4 = −9.60358e−05, A6 = −8.97426e−07,A8 = −1.12664e−08, A10 = 9.31137e−11 11th surface k = 0.000 A4 =5.78306e−07, A6 = −2.26619e−07, A8 = −3.05673e−09 12th surface k = 0.000A4 = 1.03740e−04, A6 = −2.68617e−07 19th surface k = 0.000 A4 =1.30548e−05, A6 = −2.48736e−08, A8 = −5.88997e−08 20th surface k = 0.000A4 = −3.17374e−05, A6 = −8.92951e−08 Zoom data (∞) WE ST1 TE ST2 ST3Focal length 6.07 12.74 23.52 8.23 18.77 Fno. 1.85 2.18 2.53 1.98 2.37Angle of field 2ω 77.93 39.75 21.81 59.39 7.33 fb (in air) 7.34 8.958.21 7.94 9.06 Total length (in air) 60.48 58.01 65.81 57.81 62.31 d30.30 7.65 15.93 3.02 13.00 d9 21.11 6.47 1.10 13.93 2.52 d19 3.12 6.3411.96 4.32 9.12 d21 5.19 6.79 6.04 5.78 6.90 Unit focal length f1 =49.72 f2 = −11.70 f3 = 16.42 f4 = 28.21

Numerical Example 11 Unit: mm

Surface data Surface no. r d nd νd object plane ∞ ∞  1 32.422 1.001.94595 17.98  2 24.982 3.65 1.81600 46.62  3 173.616 Variable  4 85.8771.00 1.88300 40.76  5 8.673 3.97  6* 307.488 0.80 1.58313 59.38  7*14.178 2.64  8 24.905 1.63 1.92286 20.88  9 243.771 Variable 10 (Stop) ∞0.50 11* 14.962 2.07 1.85135 40.10 12* −65.687 0.00 13 ∞ 0.10 14 6.9292.69 1.49700 81.54 15 18.683 0.59 1.80518 25.42 16 5.804 1.78 17 −22.6050.73 1.92286 20.88 18 −1284.735 2.24 1.58313 59.38 19* −10.215 Variable20* 11.801 2.62 1.49700 81.54 21 107.003 Variable 22 ∞ 0.50 1.5477162.84 23 ∞ 0.50 24 ∞ 0.50 1.51633 64.14 25 ∞ 1.01 Image plane ∞ (Lightreceiving surface) Aspherical surface data 6th surface k = 0.000 A4 =−1.59918e−04, A6 = 2.84008e−06, A8 = −4.46572e−08, A10 = 8.52526e−11 7thsurface k = 0.000 A4 = −3.00603e−04, A6 = 2.98377e−06, A8 =−7.14642e−08, A10 = 3.51419e−10 11th surface k = 0.000 A4 = 3.05204e−06,A6 = −4.79667e−07, A8 = −5.23699e−09 12th surface k = 0.000 A4 =8.81792e−05, A6 = −7.55380e−07 19th surface k = 0.000 A4 = 6.29657e−05,A6 = 1.43686e−07, A8 = −3.38587e−08 20th surface k = 0.000 A4 =−1.25621e−05, A6 = 3.85445e−07, A8 = −5.46258e−09 Zoom data (∞) WE ST1TE ST2 ST3 Focal length 6.07 12.73 23.51 8.23 18.78 Fno. 1.85 2.16 2.591.95 2.40 Angle of field 2ω 77.94 39.81 21.79 59.38 27.49 fb (in air)5.66 7.68 6.42 6.68 7.92 Total length (in air) 60.51 57.37 65.78 57.0761.41 d3 0.71 7.96 16.17 3.45 12.76 d9 21.11 6.03 1.20 13.39 1.91 d195.03 7.70 13.98 5.54 10.81 d21 3.50 5.51 4.26 4.52 5.76 Unit focallength f1 = 50.89 f2 = −11.52 f3 = 15.72 f4 = 26.44

Values in each embodiment are showed as below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Zoom ratio3.88 3.88 3.88 3.88 3.88 3.88 Total length at wide angle end 60.49 59.8961.42 60.03 60.06 60.37 Total length at telephoto end 65.85 68.50 70.6868.76 65.90 65.71 Back focus at wide angle end 7.33 5.41 5.67 5.65 5.815.84 Back focus at telephoto end 8.27 7.15 7.18 7.20 6.15 6.44 Focallength of first lens unit 50.47 49.36 55.03 54.55 50.57 50.70 Focallength of second lens unit −11.67 −10.76 −11.03 −11.10 −11.30 −11.72Focal length of third lens unit 16.15 15.93 15.85 15.67 15.49 15.94Focal length of fourth lens unit 29.71 24.31 26.32 26.48 27.59 25.70

Example 7 Example 8 Example 9 Example 10 Example 11 Zoom ratio 3.88 3.883.88 3.89 3.88 Total length at wide angle end 60.45 59.96 60.21 60.4860.51 Total length at telephoto end 65.64 65.23 65.13 65.81 65.78 Backfocus at wide angle end 6.52 5.69 6.65 7.34 5.66 Back focus at telephotoend 7.47 6.44 6.85 8.21 6.42 Focal length of first lens unit 50.52 50.8449.61 49.72 50.89 Focal length of second lens unit −11.66 −11.43 −11.93−11.70 −11.52 Focal length of third lens unit 15.93 15.48 16.15 16.4215.72 Focal length of fourth lens unit 28.05 27.67 26.68 28.21 26.44

Here, regarding the total length at wide angle end, the total length attelephoto end, the back focus at wide angle end and the back focus attelephoto end, these values are expressed in consideration of thicknessof a filter which is expressed upon air conversion of a distance.

Aberration diagrams at the time of infinite object point focusing in theembodiments from the first embodiment to the eleventh embodimentdescribed above are shown in diagrams from FIG. 12A to FIG. 22C. Inthese aberration diagrams, FIG. 12A, FIG. 13A, FIG. 14A, FIG. 15A, FIG.16A, FIG. 17A, FIG. 18A, FIG. 19A, FIG. 20A, FIG. 21A, and FIG. 22A showa spherical aberration (SA); an astigmatism (AS), a distortion, (DT),and a chromatic aberration of magnification (CC) at the wide angle end,FIG. 12B, FIG. 13B, FIG. 14B, FIG. 15B, FIG. 16B, FIG. 17B, FIG. 18B,FIG. 19B, FIG. 20B, FIG. 21B, and FIG. 22B show a spherical aberration(SA), an astigmatism (AS), a distortion (DT), and a chromatic aberrationof magnification (CC) in an intermediate focal length state, and FIG.12C, FIG. 13C, FIG. 14C, FIG. 15C, FIG. 16C, FIG. 17C, FIG. 18C, FIG.19C, FIG. 20C, FIG. 21C, and FIG. 22C show a spherical aberration (SA),an astigmatism (AS), a distortion (DT), and a chromatic aberration ofmagnification (CC) at the telephoto end. In these diagrams, ‘ω’ denotesa half angle of field.

Values of conditional expressions (1)-(20) in each embodiment are shownbelow:

SF_(3n)   Conditional expression (1)

vd₃   Conditional expression (2)

D₃/f₃   Conditional expression (3)

UY_(1 G)/f_(w)   Conditional expression (4)

UY_(3 G)/f₃   Conditional expression (5)

UY_(3 G)/f_(w)   Conditional expression (6)

f₁/f_(w)   Conditional expression (7)

|f₂/f_(w)|  Conditional expression (8)

(β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))   Conditional expression(9)

f₃/f_(w)   Conditional expression (10)

f₄/f_(w)   Conditional expression (11)

L_(w)/f_(w)   Conditional expression (12)

(β_(2t)/β_(2w))/(β_(3t)/β_(3w))   Conditional expression (13)

β_(2t)/β_(2w)   Conditional expression (14)

β_(3t)/β_(3w)   Conditional expression (15)

β_(4t)/β_(4w)   Conditional expression (16)

D_(2w)/f_(w)   Conditional expression (17)

Δ3G/f_(w)   Conditional expression (18)

IH/f_(w)   Conditional expression (19)

D_(2w)/L_(11r)   Conditional expression (20)

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Conditionalexpression (1) −0.73 −0.75 −0.73 −0.70 −0.65 −0.67 Conditionalexpression (2) 61.03 66.21 64.46 62.63 111.79 87.99 Conditionalexpression (3) 0.11 0.10 0.12 0.12 0.13 0.11 Conditional expression (4)0.27 0.27 0.27 0.27 0.27 0.27 Conditional expression (5) 0.29 0.29 0.300.31 0.31 0.30 Conditional expression (6) 0.78 0.77 0.80 0.80 0.80 0.78Conditional expression (7) 8.33 8.15 9.08 9.00 8.35 8.35 Conditionalexpression (8) 1.93 1.78 1.82 1.83 1.87 1.93 Conditional expression (9)3.88 3.88 3.88 3.88 3.88 3.88 Conditional expression (10) 2.67 2.63 2.622.59 2.56 2.63 Conditional expression (11) 4.90 4.01 4.34 4.37 4.56 4.24Conditional expression (12) 9.66 9.42 9.77 9.55 9.63 9.60 Conditionalexpression (13) 0.80 0.65 0.67 0.66 0.78 0.78 Conditional expression(14) 1.80 1.68 1.68 1.67 1.75 1.77 Conditional expression (15) 2.26 2.582.51 2.53 2.25 2.27 Conditional expression (16) 0.95 0.89 0.92 0.92 0.980.97 Conditional expression (17) 3.57 3.30 3.43 3.41 3.57 3.56Conditional expression (18) 1.59 2.08 1.95 1.93 1.62 1.62 Conditionalexpression (19) 0.76 0.76 0.76 0.76 0.76 0.76 Conditional expression(20) 0.67 0.58 0.55 0.55 0.67 0.67

Example 7 Example 8 Example 9 Example 10 Example 11 Conditionalexpression (1) −0.73 −0.56 −0.73 −0.73 −0.59 Conditional expression (2)72.78 92.53 62.70 82.09 94.62 Conditional expression (3) 0.12 0.13 0.130.13 0.11 Conditional expression (4) 0.27 0.27 0.27 0.27 0.27Conditional expression (5) 0.30 0.31 0.29 0.29 0.30 Conditionalexpression (6) 0.78 0.79 0.77 0.77 0.79 Conditional expression (7) 8.338.38 8.20 8.19 8.39 Conditional expression (8) 1.92 1.88 1.97 1.93 1.90Conditional expression (9) 3.88 3.88 3.88 3.88 3.88 Conditionalexpression (10) 2.63 2.55 2.67 2.71 2.59 Conditional expression (11)4.62 4.56 4.41 4.65 4.36 Conditional expression (12) 9.63 9.57 9.60 9.649.64 Conditional expression (13) 0.79 0.76 0.84 0.82 0.77 Conditionalexpression (14) 1.80 1.75 1.82 1.82 1.76 Conditional expression (15)2.27 2.31 2.16 2.23 2.29 Conditional expression (16) 0.95 0.96 0.99 0.950.96 Conditional expression (17) 3.56 3.56 3.57 3.56 3.56 Conditionalexpression (18) 1.56 1.60 1.57 1.60 1.60 Conditional expression (19)0.76 0.76 0.76 0.76 0.76 Conditional expression (20) 0.67 0.66 0.68 0.680.67

(Correction of Distortion)

Incidentally, when the zoom lens system of the present invention isused, a digital correction of distortion of an image is carried outelectrically. A basic concept for the digital correction of thedistortion of an image will be described below.

For example, as shown in FIG. 23, with a point of intersection of anoptical axis and an image pickup plane to be a center, a magnificationon a circumference (image height) of a circle of radius R making acontact internally with a longer side of an effective image pickup planeis fixed, and this circumference is let to be a base reference for thecorrection. Next, each point on a circumference (image height) of anarbitrary radius r(ω) other than the radius R is moved in a substantialdirection of radiation, and the correction is carried out by moving on aconcentric circle such that the radius becomes r′(ω).

For example, in FIG. 23, a point P₁ on a circumference of an arbitraryradius r₁(ω) positioned at an inner side of a circle of radius R ismoved to a point P₂ on a circumference of a radius r₁′(ω) which is to becorrected, directed toward a center of the circle. Moreover, a point Q₁on a circumference of an arbitrary radius r₂(ω) positioned at an outerside of the circle of radius R is moved to a point Q₂ on a circumferenceof a radius r₂′(ω) which is to be corrected, directed toward a directionaway from the center of the circle.

Here, r′(ω) can be expressed as follows.

r′(ω)=α·f·tan ω(0≦α≦1)

where, ω is a half angle of field of an object and f is a focal lengthof an imaging optical system (the zoom lens system in the presentinvention).

Here, when an ideal image height corresponding to a circle (imageheight) of radius R is let to be Y, then

α=R/Y=R/(f·tan ω).

The optical system, ideally, is rotationally symmetric with respect toan optical axis. In other words, the distortion also occurs in arotationally symmetric manner with respect to the optical axis.Consequently, as it has been described above, in a case of correctingelectrically the optical distortion, when it is possible to carry outcorrection by fixing a magnification on a circumference (image height)of the circle of radius R making a contact internally with a longer sideof the effective image pickup plane, with a point of intersection of anoptical axis on a reproduced image, and an image pickup plane to be acenter, and moving each point on the circumference (image height) ofradius r(ω) other than the radius R in a substantial direction ofradiation, and moving on a concentric-circle such that the radiusbecomes r′(ω), it can be considered to be advantageous from a point ofamount of data and amount of calculation.

Incidentally, an optical image ceases to be a continuous amount at apoint of time when an image is picked up by an electronic image pickupelement (due to sampling). Consequently, the circle of radius R which isdrawn exactly on the optical image ceases to be an accurate circle aslong as pixels on the electronic image pickup element are not arrangedradially.

In other words, regarding a shape correction of image data expressed foreach discrete coordinate point, a circle which can fix the magnificationdoes not exist. Therefore, for each pixel (Xi, Yj), a method ofdetermining coordinates of a destination of movement (Xi′, Yj′) may beused. When two or more points (Xi, Yj) have moved to the coordinates(Xi′, Yj′), an average of values of each pixel is taken. Moreover, whenthere is no point which has moved, interpolation may be performed byusing a value of coordinate (Xi′, Yj′) of some of the surroundingpixels.

Such method is effective for correction when the distortion with respectto the optical axis is remarkable due to a manufacturing error etc. ofthe optical system or the electronic image pickup element, in theelectronic image pickup apparatus having the zoom lens system inparticular, and when the circle of the radius R drawn on the opticalimage is asymmetric. Moreover, it is effective for correction when thereoccurs to be a geometric distortion at the time of reproducing a signalto an image in an image pickup element or various output devices.

In the electronic image pickup apparatus of the present invention, forcalculating a correction amount r′(ω)−r(ω), an arrangement may be madesuch that a relationship between r(ω), in other words, half angle offield and the image height, or a relationship between a real imageheight r and an ideal image height r′/α is recorded in a recordingmedium which is built-in in the electronic image pickup apparatus.

For an image after the distortion correction, not to have an extremeshortage of an amount of light at both ends in a direction of shortside, the radius R may satisfy the following conditional expression.

0≦R≦0.6 Ls

where, Ls is a length of a short side of the effective image pickupsurface.

It is preferable that the radius R satisfies the following conditionalexpression.

0.3 Ls R≦0.6 Ls

Furthermore, it is most advantageous to match the radius R with a radiusof a circle making an internal contact in a short side direction of asubstantially effective image pickup plane. In a case of correction inwhich, the magnification is fixed near the radius R=0, in other words,near on the axis, it is somewhat disadvantageous from an aspect ofsubstantial number of images, but it is possible to secure an effect formaking the size small even when the angle is widened.

A focal length interval which requires a correction is divided into anumber of focal point zones. Moreover, the correction may be carried outwith the amount of correction as in a case in which, a correction resultwhich satisfies substantially the following relationship

r′(ω)=α·f·tan ω

near a telephoto end in the focal point zones which are divided.

However, in this case, at a wide angle end in the focal point zoneswhich are divided, a barrel-shape distortion at the wide angel end ofthe focal point zones which are divided is remained to some extent.Moreover, when the number of divided zones is increased, there arises aneed to hold specific data necessary for correction, additionally in arecording medium. Therefore it is not preferable to increase the numberof divided zones. Therefore, one or a plurality of coefficientsassociated with each focal length in the focal point zones which aredivided, are calculated in advance. The coefficients may be determinedbased on a measurement by simulation or by actual equipment.

An amount of correction in a case in which, the correction result whichsatisfies substantially the following relationship

r′(ω)=α·f·tan ω

near the telephoto end in the focal point zones which are divided may becalculated, and may let to be a final amount of correction bymultiplying uniformly the coefficient for each focal length with respectto this amount of correction.

Incidentally, when there is no distortion in an image achieved byimaging (forming an image) of an infinite object, the followingrelationship

f=y/tan ω

holds.

Here, y denotes a height (image height) of an image point from theoptical axis, f denotes a focal length of an imaging system (zoom lenssystem in the present invention), and ω denotes an angle (object halfangle of field) with respect to the optical axis in an object pointdirection corresponding to image points connecting from a center on animage pickup plane up to a position of y.

When there is a barrel-shape distortion in the imaging system, therelationship becomes

f>y/tan ω.

In other words, when the focal length f of the imaging system, and theimage height y are let to be fixed, a value of ω becomes large.

(Digital Camera)

FIG. 24 to FIG. 26 are conceptual diagrams of a structure of a digitalcamera according to the present invention in which a zoom lens systemdescribed above is incorporated in a taking optical system 141. FIG. 24is a front perspective view showing an appearance of a digital camera140, FIG. 25 is a rear view of the same, and FIG. 26 is a schematiccross-sectional view showing a structure of the digital camera 140. InFIG. 24 and FIG. 26, show an uncollapsed state of the taking opticalsystem 141. The digital camera 140, in a case of this example, includesthe taking optical system 141 having a taking optical path 142, a finderoptical system 143 having a finder optical path 144, a shutter button145, a flash 146, a liquid-crystal display monitor 147, a focal-lengthchanging button 161, and a setting changing switch 162 etc., and in theuncollapsed state of the taking optical system 141, by sliding a cover160, the taking optical system 141, the finder optical system 143, andthe flash 146 are covered by the cover 160. Further, when the cover 160is opened and the digital camera is set in a photo taking state, thetaking optical system 141 assumes the uncollapsed state as shown in FIG.26, when the shutter button 145 disposed on an upper portion of thedigital camera 140 is pressed, in synchronization with the pressing ofthe shutter button 145, a photograph is taken by the taking opticalsystem 141 such as the zoom lens system in the first embodiment. Anobject image formed by the taking optical system 141 is formed on animage pickup surface of a CCD 149 via a cover glass C and a low passfilter on which a wavelength region restricting coating is applied. Anobject image which is received as light by the CCD 149 is displayed onthe liquid-crystal display monitor 147 which is provided on a rearsurface of the digital camera 140 as an electronic image, via aprocessing means 151. Moreover, a recording means 152 is connected tothe processing means 151, and it is also possible to record theelectronic image which is taken. The recording means 152 may be providedseparately from the processing means 151, or may be formed by recordingby writing electronically in a flexible disc, a memory card, or an MOetc. Moreover, the camera may be formed as a silver-salt camera in whicha silver-salt film is disposed instead of the CCD 149.

Furthermore, a finder objective optical system 153 is disposed on thefinder optical path 144. The finder objective optical system 153consists of a plurality of lens units (three units in the diagram), andtwo prisms, and is made of a zoom optical system in which a focal lengthchanges in synchronization with a zoom lens system of the taking opticalsystem 141. An object image formed by the finder objective opticalsystem 153 is formed on a field frame 157 of an erecting prism 155 whichis an image erecting member. On a rear side of the erecting prism 155,an eyepiece optical system 159 which guides an erected image to aviewer's eyeball, is disposed. A cover member 150 is disposed on anemergence side of the eyepiece optical system 159.

Since the digital camera 140 structured in such manner has the takingoptical system 141 according to the present invention, has an extremelysmall thickness in collapsed state, and an extremely stable imagingperformance in the entire zooming region at high magnification, it ispossible to realize a high-performance, a small size, and a widening ofangle of field.

(Internal Circuit Structure)

FIG. 27 is a structural block diagram of an internal circuit of maincomponents of the digital camera 140. In the following description, theprocessing means 151 described above includes for instance, a CDS/ADCsection 124, a temporary storage memory 117, and an image processingsection 118, and a storage means 152 consists of a storage mediumsection 119 for example.

As shown in FIG. 27, the digital camera 140 includes an operatingsection 112, a control section 113 which is connected to the operatingsection 112, the temporary storage memory 117 and an imaging drivecircuit 116 which are connected to a control-signal output port of thecontrol section 113, via a bus 114 and a bus 115, the image processingsection 118, the storage medium section 119, a display section 120, anda set-information storage memory section 121.

The temporary storage memory 117, the image processing section 118, thestorage medium section 119, the display section 120, and theset-information storage memory section 121 are structured to be capableof mutually inputting and outputting data via a bus 122. Moreover, theCCD 149 and the CDS/ADC section 124 are connected to the imaging drivecircuit 116.

The operating section 112 includes various input buttons and switches,and is a circuit which informs the control section, event informationwhich is input from outside (by a user of the digital camera) via theseinput buttons and switches.

The control section 113 is a central processing unit (CPU), and has abuilt-in computer program memory which is not shown in the diagram. Thecontrol section 113 is a circuit which controls the entire digitalcamera 140 upon receiving instructions and commands input by the user ofthe camera via the operating section 112, according to a computerprogram stored in this computer program memory.

The CCD 149 receives as light an object image which is formed via thetaking optical system 141 according to the present invention. The CCD149 is an image pickup element which is driven and controlled by theimaging drive circuit 116, and which converts an amount of light foreach pixel of the object image to an electric signal, and outputs to theCDS/ADC section 124.

The CDS/ADC section 124 is a circuit which amplifies the electric signalwhich is input from the CCD 149, and carries out analog/digitalconversion, and outputs to the temporary storage memory 117 image rawdata (bare data, hereinafter called as ‘RAW data’) which is onlyamplified and converted to digital data.

The temporary storage memory 117 is a buffer which includes an SDRAM(Synchronous Dynamic Random Access Memory) for example, and is a memorydevice which stores temporarily the RAW data which is output from theCDS/ADC section 124. The image processing section 118 is a circuit whichreads the RAW data stored in the temporary storage memory 117, or theRAW data stored in the storage medium section 119, and carries outelectrically various image-processing including the distortioncorrection, based on image-quality parameters specified by the controlsection 113.

The storage medium section 119 is a recording medium in the form of acard or a stick including a flash memory for instance, detachablymounted. The storage medium section 119 is a control circuit of a devicein which, the RAW data transferred from the temporary storage memory 117and image data subjected to image processing in the image processingsection 118 are recorded and maintained in the card flash memory and thestick flash memory.

The display section 120 includes the liquid-crystal display monitor, andis a circuit which displays images and operation menu on theliquid-crystal display monitor. The set-information storage memorysection 121 includes a ROM section in which various image qualityparameters are stored in advance, and a RAM section which stores imagequality parameters which are selected by an input operation on theoperating section 112, from among the image quality parameters which areread from the ROM section. The set-information storage memory section121 is a circuit which controls an input to and an output from thememories.

The digital camera 140 structured in such manner has the taking opticalsystem 141, according to the present invention, which, while having asufficient wide angle region, and a compact structure, has an extremelystable imaging performance in the entire magnification region at a highmagnification. Therefore, it is possible to realize the highperformance, the small size, and widening of the angle. Moreover, aprompt focusing operation at the wide angle side and the telephoto sideis possible.

As it has been described above, the present invention is useful for azoom lens system in which, it is easy to have a favorable image formingperformance while securing an angle of field, a zooming ratio, and an Fvalue.

According to the present invention, it is possible to provide a zoomlens system in which, it is easy to have a favorable image formingperformance while securing the angle of field, the zooming ratio, andthe F value.

Furthermore, it is possible to provide an image pickup apparatus whichincludes such zoom lens system.

1. A zoom lens system comprising in order from an object side to animage side: a first lens unit having a positive refracting power; asecond lens unit having a negative refracting power; a third lens unithaving a positive refracting power; and a fourth lens unit having apositive refracting power, wherein at the time of zooming from a wideangle end to a telephoto end, distances between the lens units change,and the third lens unit comprises a first cemented lens component havinga concave image-side surface on the image side, and a second cementedlens component having a concave object-side surface on the object side,which is disposed immediately after the image side of the first cementedlens component, and the first cemented lens component includes apositive lens, and a negative lens having a concave image-side surfacewhich is disposed on the image side of the positive lens, and the secondcemented lens component includes a negative lens having a concaveobject-side surface on the object side, and a positive lens which isdisposed on the image side of the negative lens.
 2. The zoom lens systemaccording to claim 1, wherein the first cemented lens component has ameniscus shape convex to the object side, and the second cemented lenscomponent has a meniscus shape convex to the image side.
 3. The zoomlens system according to claim 1, wherein the first cemented lenscomponent and the second cemented lens component satisfy the followingconditional expression (1)−0.9<SF _(3n)<−0.1   (1) where, SF_(3n) is defined bySF_(3n)=(32R_(1r)+33R_(2f))/(32R_(1r)−33R_(2f)), where 32R_(1r) denotesa radius of curvature on the image side of the first cemented lenscomponent in the third lens unit, and 33R_(2f) denotes a radius ofcurvature on the object side of the second cemented lens component inthe third lens unit.
 4. A zoom lens system comprising in order from anobject side to an image side: a first lens unit having a positiverefracting power; a second lens unit having a negative refracting power;a third lens unit having a positive refracting power; and a fourth lensunit having a positive refracting power, wherein at the time of zoomingfrom a wide angle end to a telephoto end, distances between the lensunits change, and the third lens unit comprises a first cemented lenscomponent, and a second cemented lens component which is disposed on theimage side of the first cemented lens component, and the first cementedlens component comprises a positive lens, and a negative lens which isdisposed on the image side of the positive lens, and the second cementedlens components comprises a negative lens, and a positive lens which isdisposed on the image side of the negative lens, and the first cementedlens component and the second cemented lens component satisfy thefollowing conditional expression (2)50<vd₃<120   (2) where, vd₃ is defined byvd₃₌(vdL_(32p)+vdL_(33p))−(vdL_(32n)+vdL_(33p)), where, vdL_(32p)denotes Abbe constant for d-line of the positive lens of the firstcemented lens component in the third lens unit, vdL_(33p) denotes Abbeconstant for d-line of the positive lens of the second cemented lenscomponent in the third lens unit, vdL_(32n) denotes Abbe constant ford-line of the negative lens of the first cemented lens component in thethird lend unit, and vdL_(33p) denotes Abbe constant for d-line of thenegative lens of the second cemented lens component in the third lensunit.
 5. The zoom lens system according to claim 1, wherein the firstcemented lens component and the second cemented lens component satisfythe following conditional expression (2)50<vd₃<120   (2) where, vd₃ is defined byvd₃=(vdL_(32p)+vdL_(33p))−(vdL_(32n)+vdL_(33n)), where, vdL_(32p)denotes Abbe constant for d-line of the positive lens of the firstcemented lens component in the third lens unit, vdL_(33p) denotes Abbeconstant for d-line of the positive lens of the second cemented lenscomponent in the third lens unit, vdL_(32n) denotes Abbe constant ford-line of the negative lens of the first cemented lens component in thethird lend unit, and vdL_(33n) denotes Abbe constant for d-line of thenegative lens of the second cemented lens component in the third lensunit.
 6. The zoom lens system according to claim 1, wherein the firstcemented lens component and the second cemented lens component aredisposed side-by-side leaving a space between the first cemented lenscomponent and the second cemented lens component, and satisfy thefollowing conditional expression (3)0.08<D ₃ /f ₃<0.20   (3) where, D₃ denotes a distance on an optical axisbetween the first cemented lens component and the second cemented lenscomponent in the third lens unit, and f₃ denotes a focal length of thethird lens unit.
 7. The zoom lens system according to claim 1, whereinthe second cemented lens component is disposed nearest to the imageside, in the third lens unit, and the positive lens in the secondcemented lens component has an aspheric image-side surface which isconvex on the image side.
 8. The zoom lens system according to claim 1,wherein the third lens unit comprises in order from the object side, apositive single lens having a positive refracting power, the firstcemented lens component, and the second cemented lens component, and thepositive single lens comprises at least one aspheric surface.
 9. Thezoom lens system according to claim 1, wherein the zoom lens systemsatisfies the following conditional expressions (4) and (5)0.26<UY _(1G) /f _(w)<0.28   (4)0.25<UY _(3G) /f ₃<0.5   (5) where, f_(w) denotes a focal length of theoverall zoom lens system at the wide angle end, UY_(1G) denotes a heightfrom an optical axis of axial marginal light rays at a surface on theobject side of the first lens unit, at the wide angle end, UY_(3G)denotes a height from an optical axis of axial marginal rays at asurface on the object side of the third lens unit, at the wide angleend, and f₃ is a focal length of the third lens unit.
 10. The zoom lenssystem according to claim 1, wherein the zoom lens system satisfies thefollowing conditional expressions (4) and (6)0.26<UY _(1G) /f _(w)<0.28   (4)0.60<UY _(3G) /f _(w)<1.00   (6) where, f_(w) denotes the focal lengthof the overall zoom lens system at the wide angle end, UY_(1G) denotesthe height from an optical axis of axial marginal light rays at asurface on the object side of the first lens unit, at the wide angleend, and UY_(3G) denotes the height from an optical axis of axialmarginal rays at a surface on the object side of the third lens unit, atthe wide angle end.
 11. The zoom lens system according to claim 1,wherein the zoom lens system satisfies the following conditionalexpression (7)7.0<f ₁ /f _(w)<10   (7) where, f₁ denotes a focal length of the firstlens unit, and f_(w) denotes the focal length of the overall zoom lenssystem at the wide angle end.
 12. The zoom lens system according toclaim 1, wherein the zoom lens system satisfies the followingconditional expressions (8) and (9)1.6<|f ₂ /f _(w)|<2.1   (8)3.5<((β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))<5.0   (9) where, f₂denotes a focal length of the second lens unit, f_(w) denotes the focallength of the overall zoom lens system at the wide angel end, β^(2w) andβ_(2t) denote a lateral magnification of the second lens unit, at thewide angle end and the telephoto end respectively, β_(3w) and β_(3t)denote a lateral magnification of the third lens unit, at the wide angleend and the telephoto end respectively, and β_(4w) and β_(4t) denote alateral magnification of the fourth lens unit, at the wide angle end andthe telephoto end respectively.
 13. The zoom lens system according toclaim 1, wherein the zoom lens system satisfies the followingconditional expression (10)2.0<f ₃ /f _(w)<3.0   (10) where, f₃ denotes the focal length of thethird lens unit, and f_(w) denotes the focal length of the overall zoomlens system at the wide angle end.
 14. The zoom lens system according toclaim 1, wherein the zoom lens system satisfies the followingconditional expression (11)3.4<f ₄ /f _(w)<5.5   (11) where, f₄ denotes a focal length of thefourth lens unit, and f_(w) denotes the focal length of the overall zoomlens system at the wide angle end.
 15. The zoom lens system according toclaim 1, wherein the zoom lens system satisfies the followingconditional expression (12)9.0<L _(w) /f _(w)<10.2   (12) where, L_(w) denotes a distance along anoptical axis from a surface on the object side of the first lens unit upto an image plane at the wide angle end when a back focus is let to bean air conversion distance, and f_(w) denotes the focal length of theoverall zoom lens system at the wide angle end.
 16. The zoom lens systemaccording to claim 1, wherein the second lens unit comprises in orderfrom the object side, a negative meniscus lens component, a negativelens component, and a positive lens component, and the total number oflens components in the second lens unit is 3, and the second lens unitsatisfies the following conditional expressions (13) and (9)0.5<(β_(2t)/β_(2w))/(β_(3t)/β_(3w))<1.0   (13)3.5<(β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))<5.0   (9) where,β_(2w) and β_(2t) denote a lateral magnification of the second lensunit, at the wide angle end and the telephoto end respectively, β_(3w)and β_(3t) denote a lateral magnification of the third lens unit, at thewide angle end and the telephoto end respectively, and β_(4w) and β_(4t)denote a lateral magnification of the fourth lens unit, at the wideangle end and the telephoto end respectively.
 17. The zoom lens systemaccording to claim 1, wherein the zoom lens system satisfies thefollowing conditional expression (14)1.4<β_(2t)/β2w<2.1   (14) where, β_(2w) and β_(2t) denote lateralmagnification of the second lens unit, at the wide angle end and thetelephoto end respectively.
 18. The zoom lens system according to claim1, wherein the zoom lens system satisfies the following conditionalexpression (15)1.8<β_(3t)/β^(3w)<2.9   (15) where, β_(3w) and β_(3t) denote a lateralmagnification of the third lens unit, at the wide angle end and thetelephoto end respectively.
 19. The zoom lens system according to claim1, wherein the zoom lens system satisfies the following conditionalexpression (16)0.6<β_(4t)/β^(4w)<1.3   (16) where, β_(4w) and β_(4t) denote a lateralmagnification of the fourth lens unit, at the wide angle end and thetelephoto end.
 20. The zoom lens system according to claim 1, whereinthe zoom lens system satisfies the following conditional expressions(17) and (9)2.8<D _(2w) /f _(w)<4.2   (17)3.5<(β_(2t)/β_(2w))×(β_(3t)/β_(3w))×(β_(4t)/β_(4w))<5.0   (9) where,D_(2w) denotes an air distance on an optical axis between the secondlens unit and the third lens unit at the wide angle end, f_(w) denotesthe focal length of the overall zoom lens system at the wide angle end,β_(2w) and β_(2t) denote a lateral magnification of the second lensunit, at the wide angle end and the telephoto end respectively, β^(3w)and β_(3t) denote a lateral magnification of the third lens unit, at thewide angle end and the telephoto end respectively, and β_(4w) and β_(4t)denote a lateral magnification of the fourth lens unit, at the wideangle end and the telephoto end respectively.
 21. The zoom lens systemaccording to claim 1, wherein the zoom lens system satisfies thefollowing conditional expression (18)1.3<Δ3G/f _(w)<2.4   (18) where, Δ3G denotes an amount of movement ofthe third lens unit from the wide angle end to the telephoto end, andf_(w) denotes the focal length of the overall zoom lens system at thewide angle end.
 22. The zoom lens system according to claim 1,comprising: an aperture stop which is disposed immediate before theobject side of the third lens unit, wherein the aperture stop, at thetime of zooming from the wide angle end to the telephoto end, movesintegrally with the third lens unit.
 23. The zoom lens system accordingto claim 1, wherein the first lens unit includes one lens component, andsatisfies the following conditional expressions (19) and (20)0.725<IH/f _(w)<0.8   (19)−1.0<D _(2w) /L _(11r)<1.0   (20) where, IH denotes the maximum lightray height of off-axis rays at an image plane, f_(w) denotes a focallength of the overall zoom lens system at the wide angle end, D_(2w)denotes an air distance on an optical axis between the second lens unitand the third lens unit at the wide angle end, and L_(11r) denotes aradius of curvature of a surface nearest to the image side of the firstlens unit.
 24. The zoom lens system according to claim 1, wherein thesecond lens unit comprises a lens having an aspheric surface.
 25. Thezoom lens system according to claim 1, wherein the fourth lens unitcomprises a lens having an aspheric surface.
 26. An image pickupapparatus comprising: a zoom lens system according to claim 1; and animage pickup element, which is disposed on an image side of the zoomlens system, and which converts an image formed by the zoom lens system,to an electric signal.